Twitter may have established itself as the go-to "microblogging" site in the U.S., but it's been surpassed in China by a service called Sina Weibo. The site has been called a Twitter "copycat," but analyst Bill Bishop at Business Insider calls it "a better designed and more stable product." Here, a brief guide to China's version of Twitter:

What is Weibo?
Weibo — which literally means "microblog" — is a division of internet company Sina Corp., which runs a portal similar to Yahoo! that is the third most popular site in China. About 87 percent of the time spent on microblogging sites in China is on Weibo. (See an overview of Sina Weibo)

How big is it?
The service had 50 million members in October, and analysts predict it will reach 120 million by 2012, according to Fan Wenxin in Bloomberg Businessweek.

How similar is it to Twitter?
Yes. As with Twitter, users can post their own comments, and follow those of others. And like the American original, Weibo limits posts to 140 characters — "though in Chinese, in which many words are just two or three characters, a lot more can be expressed under that constraint than in English," says Wenxin in Bloomberg Businessweek. And just as "tweet" has become a verb in English, "zhi weibo" has become one in Chinese.

So is it just a knockoff?
No. The site integrates photos and video better than Twitter. And users can do more than just reply to or retweet other messages. "We did a lot of enhancements and innovations," says Sina CEO Charles Chao, as quoted in TIME. "It's more like a combination of Twitter and some features from Facebook." The Twitter team could actually "learn a lot" from Weibo, says Bishop at Business Insider.

How did Weibo become so popular?
China's government blocked Twitter in 2009, ahead of the 20th anniversary of the Tiananmen Square protests. Facebook was blocked soon after. That "vacuum" inspired Sina to launch Weibo in August 2009, earlier than other Chinese rivals. Several Chinese celebrities have started using the site, which has helped expand its fan base.

Is Weibo censored by the Chinese government?
Yes. When New York Times columnist Nicholas Kristof opened an account and mentioned the 1989 Tiananmen Square crackdown and the banned spiritual movement Falun Gong, his account was quickly canceled. Censors have scrutinized posts from the U.S. Embassy's account and recently banned the name of the U.S. ambassador to China, according to The Wall Street Journal.

But has it helped promote free speech?
Yes. Despite the censorship, the site is being hailed as "by far the best platform for free speech" in the country. Weibo "is now a top information source for many Chinese," says Wenxin in Bloomberg Businessweek, and it is "often an outlet for the controversial topics avoided by state-controlled media."

Sources: Bloomberg Businessweek, Business Insider, TIME, Wall St. Journal