Google designed the service, unveiled on Tuesday, to tie together all of its online properties, laying the foundation for a full-fledged social network. It is the company's biggest foray into social networking since co-founder Larry Page took over as chief executive in April.
Page has made social networking a top priority at the world's No 1 Internet search engine, whose position as the main gateway to online information could be at risk as people spend more time on sites like Facebook and Twitter.
To set its service apart from Facebook, which has more than 500 million users, Google is betting on what it says is a better approach to privacy, a hot-button issue that has burned Facebook, as well as Google, in the past.
Central to Google Plus are so-called "circles" of friends and acquaintances. Users can organize contacts into different customized circles -- family members, co-workers or college friends, say -- and share photos, videos or other information only within those smaller groups.
"In the online world there's this 'share box' and you type into it and you have no idea who is going to get that, or where it's going to land, or how it's going to embarrass you six months from now," said Google Vice President of Product Management Bradley Horowitz.
"For us, privacy isn't buried six panels deep," he added.
Facebook, which has been criticized for confusing privacy controls, introduced a feature last year that lets users create smaller groups of friends. Google, without mentioning Facebook by name, said other social networking services' attempts to create groups were "bolt-on" efforts that do not work as well.
Google Plus will be rolled out to a limited number of users in what the company is calling a field trial. Only those invited to join will initially be able to use the service. Google did not say when it would be more widely available.
LEARNING FROM BUZZ
Google's stock has been pressured by concerns about rising spending within the company and increasing regulatory scrutiny -- not to mention its struggles with social networking. The U.S. Federal Trade Commission, among others, is currently reviewing its business practices.
Its shares are down almost 20 percent this year after underperforming the market in 2010.
To create Google Plus, the company went back to the drawing board in the wake of several notable failures, including Google Wave and Google Buzz, a microblogging service whose launch was marred by privacy snafus.
"We learned a lot in Buzz, and one of the things we learned is that there's a real market opportunity for a product that addresses people's concerns around privacy and how their information is shared," said Horowitz.
Google, with $29 billion in revenue last year, drew more than 1 billion visitors worldwide to its websites in May, more than any other company, according to Web analytics firm comScore. But people are spending more time on Facebook: The average U.S. visitor spent 375 minutes on Facebook in May, compared with 231 minutes for Google.
Google Plus seems designed to make its online properties a pervasive part of the daily online experience, rather than being spots where Web surfers occasionally check in to search for a website or check email.
As with Facebook's service, Google Plus has a central Web page that displays an ever-updating stream of the comments, photos and links being shared by friends and contacts.
A toolbar across the top of most of Google's sites -- such as its main search page, its Gmail site and its Maps site - allows users to access their personalized data feed. They can then contribute their own information to the stream.
Google Plus will also offer a special video chat feature, in which up to 10 people can jump on a conference call. And Google will automatically store photos taken on cell phones on its Internet servers, allowing a Google Plus user to access the photos from any computer and share them.
When asked if he expected people to switch from Facebook to Google Plus, Google Senior Vice President of Engineering Vic Gundotra said people may decide to use both.
"People today use multiple tools. I think what we're offering here offers some very distinct advantages around some basic needs," he said.