Facebook launched a search engine Tuesday for shared content as a way to find out more about friends on the huge social network in a potential challenge to Google and other Internet firms.

"We look at Facebook as a big social database," chief executive Mark Zuckerberg said in announcing the so-called "graph search" function. "Just like any database, you should be able to query it."

The search engine aims to help members better navigate the vast amount of information on Facebook, which is not available on Web search engines such as Google.

Facebook emphasized that the new effort is not Web search, but can help find certain information archived within the network and in the content of friends.

"Every piece of content on Facebook has its own audience, and most content isn't public," a Facebook statement said.

"We've built Graph Search from the start with privacy in mind, and it respects the privacy and audience of each piece of content on Facebook. It makes finding new things much easier, but you can only see what you could already view elsewhere on Facebook."

Zuckerberg said that Facebook will also use its partnership with Microsoft's Bing search engine for the new effort and to find content housed outside the social network.

"I don't necessarily think a lot of people will be coming to Facebook to do Web search because of this, but it is a very good search engine," he said.

He said Facebook had discussed working with Google but that "Microsoft was just more willing to do things that were specific to Facebook."

The social network offered examples of graph search queries including "friends who live in my city," "people from my hometown who like hiking," "friends of friends who have been to Yosemite National Park," "software engineers who live in San Francisco and like skiing," "people who like things I like," or "people who like tennis and live nearby."

Zuckerberg said the tool is aimed at "giving the people the power and tools to take any cut of the graph (of data) they want and make any query they want."

He added that "We are not indexing the Web here, we are indexing our map of the graph."

The company said the new function goes back to its original goals of helping people make connections.

"When Facebook first launched, the main way most people used the site was to browse around, learn about people and make new connections," the statement said.

"Graph Search takes us back to our roots and allows people to use the graph to make new connections."

Tech analyst Jeff Kagan said the new Facebook effort is a modest challenge to Google.

"If I were Google, I would see this as a Facebook warning shot across their bow. This is not an immediate attack, but nevertheless an attack is coming," Kagan said.

"Can Facebook transform the search engine world? If the answer is yes than this is a bigger threat to Google."

Forrester Research analyst Nate Elliott said Facebook's initiative aims to get people more engaged on the social network.

"Facebook's worst nightmare is a static social graph; if users aren't adding very many new friends or connections... their personal network becomes less and less active over time," Elliott said.

"But that may be happening: We haven't seen significant growth in the average number of friends per user recently. Graph search seems designed to encourage users to add more friends more quickly. If it means users' personal networks change more frequently, and become more active, then that keeps them coming back to the site -- which is vital to Facebook's success."