Remember Google Buzz? What about Orkut, or Google Wave?

Google has tried several times, without much success, to take on Facebook and master social networking. Now it is making its biggest effort yet.

On Tuesday, Google introduced a social networking service called the Google+ project — which happens to look a lot like Facebook. The service, which is initially available to a select group of Google users who will soon be able to invite others, will let people share and discuss status updates, photos and links, much as they do on Facebook.

But the Google+ project will be different in one significant way, which Google hopes will be enough to convince people to use yet another social network.

It is meant for sharing with groups — like colleagues, roommates or hiking friends — not with all of one’s friends or the entire Web. It also offers group text messaging and video chat.

“In real life, we have walls and windows and I can speak to you knowing who’s in the room, but in the online world, you get to a ‘Share’ box and you share with the whole world,” said Bradley Horowitz, a vice president for product management at Google, who is leading the company’s social efforts with Vic Gundotra, a senior vice president for engineering. “We have a different model.”

When it comes to social networking, Google finds itself in an unusual position, one that its competitors in Web search know all too well: playing catch-up with a service that dominates the market.

The debut of Google+ will test whether Google can overcome its past stumbles in this area and deal with one of the most pressing challenges facing the company. At stake is Google’s status as the most popular entry point to the Web. When people post on Facebook, which is mostly off-limits to search engines, Google loses valuable information that could benefit its Web search, advertising and other products.

But Google+ may already be too late. In May, 180 million people visited Google sites, including YouTube, compared with 157.2 million on Facebook, according to comScore. But Facebook users looked at 103 billion pages and spent an average of 375 minutes on the site, while Google users viewed 46.3 billion pages and spent 231 minutes.

Advertisers pay close attention to those numbers — and to the fact that people increasingly turn to Facebook and other social sites like Twitter to ask questions they used to ask Google, like a recommendation for a restaurant or doctor.

Analysts say that Facebook users are unlikely to duplicate their network of friends on Google+ and post to both sites, but that they could use them for different types of communication. Google+ could also attract Facebook holdouts who have been uncomfortable sharing too publicly.

“Can someone eclipse Facebook in terms of its hold? It is a fantastic broadcast mechanism,” said Charlene Li, a social media analyst and founder of Altimeter Group, a technology research firm. “But if Google becomes the owner of your private groups, it’s going to be a splintering of our social lives.”

Mr. Gundotra and Mr. Horowitz said that knowing more about individual Google users would improve all Google products, including ads, search, YouTube and maps, because Google will learn what people like and eventually personalize those products.

“To think we could achieve Google’s stated mission of organizing the world’s information absent people would be ludicrous,” Mr. Horowitz said.

But Google has been criticized for failing to understand the importance of social information on the Web until competitors like Facebook and Twitter had already leapt ahead.

Larry Page, Google’s co-founder, regrets Google’s failure to lead in this market and has spent time working with the team since he became chief executive in April, people at the company say. He promoted Mr. Gundotra to senior vice president this year, placing him on an equal level with the heads of Google’s core products like search and ads.

Part of the blame, analysts say, falls on Google’s engineering-heavy culture, which values quantitative data and algorithms over more abstract pursuits like socializing.

Exhibit A is Buzz, a sharing tool for Gmail users. It automatically included users’ e-mail contacts in their Buzz network, setting off widespread criticism that Google had invaded the privacy of users and failed to understand that people’s e-mail contacts are not necessarily their friends.

Google quickly changed the service so it did not automatically connect people. In March, Google settled with the Federal Trade Commission over charges of deceptive privacy practices related to Buzz and agreed to 20 years of audits.

Mr. Gundotra and Mr. Horowitz, both of whom worked on Buzz, say they were chastened by the experience. Google+ grew out of those mistakes, they said, because they realized how much people care about controlling the information they share.

And unlike its approach with Buzz, which was tested only by Google employees before its broad introduction to the public, Google is calling Google+ a project, as a way to emphasize that it is not a final product. The company says it will undergo many changes to fix problems and introduce features. Still, its new Web site, plus.google.com, is Google’s most fully formed social networking tool yet.

Mr. Gundotra and Mr. Horowitz said they took pains to mimic people’s relationships in real life and eliminate the social awkwardness that things like friend requests and oversharing can generate on other sites.

Google+ users will start by selecting people they know from their Gmail contacts (and from other services, once Google strikes deals with them). They can drag and drop friends’ names into different groups, or circles, and give the circles titles, like “sisters” or “book club.” Then they can share with these groups or with all of their friends.

Unlike on Facebook, people do not have to agree to be friends with one another. They can receive someone’s updates without sharing their own.

Facebook has also recognized people’s desire to share with smaller groups, and last year introduced Groups to make that possible. It has been one of Facebook’s fastest-growing products, with users creating 50 million groups in the first six months, according to Facebook.

“We’re in the early days of making the Web more social, and there are opportunities for innovation everywhere,” a Facebook spokeswoman said in response to Google+.

When users visit their Google+ home page, they see three columns and a stream of status updates in the middle that looks remarkably like Facebook. But Google said that besides an easier way to share with select groups, Google+ has several other features that distinguish it from competitors.

It offers group video chats, called Hangouts, that other members of a group can join as it is happening. Users can search a section called Sparks to see articles and videos from across the Web on certain topics, like recipes or ailments, and share them with relevant groups of friends.

And on the Google+ mobile app for Android phones and iPhones, people can chat with groups using a feature called Huddle. Photos and videos shot with cellphones are automatically uploaded to a private album, so Google+ users can quickly view and post them from their phones or later on a computer.

With these services, Google will compete with a host of start-ups, like Path for sharing with small groups, SocialEyes for video chat, Flipboard for articles on certain topics and GroupMe for group texting.

“The notion that online sharing is broken is not an insight that is unique to us,” Mr. Horowitz said.

“We have a way to bring in millions of users in a way that is challenging for a start-up.”