Near the end of August, President Obama's campaign trail swung through a curious community. He stood before the digital crowds of Reddit.com and called out, "Hi, I'm Barack Obama, president of the United States. Ask me anything."

If this call for questions had rung out over Facebook or Twitter, it wouldn't have made much of a stir. Major social media sites have played a key role in both the 2008 and current presidential elections. But Reddit?

The social news site is a far cry from the omnipresent, family-friendly pages of Facebook and the pithy, personality-driven ethos of Twitter. But Reddit has a huge following among a particular breed of Web-savvy readers. Its warren of links, discussion forums, and Ask Me Anything interviews (or AMAs) racks up 3 billion page views a month.

Mr. Obama's interview could be a turning point for the seven-year-old site. Oprah Winfrey introduced Twitter to a mainstream audience in 2009 when she posted her first "tweet" on daytime TV. Now, the president's virtual visit may have hoisted Reddit's growing influence and further legitimized its highly successful AMA format.

"In the early days, we needed to book – convince – celebrities to participate," says Erik Martin, general manager of Reddit. "Then, maybe three years ago, it just started to happen without any involvement from us whatsoever."

This critical mass has pulled in musicians, writers, politicians, Hollywood stars, and online celebrities. But Mr. Martin says many of the best AMAs come from obscure people with interesting perspectives. Perennial listmaker Buzzfeed.com listed among its all-time favorites "I saved a girl from drowning. She then sued me. AMA." and "[I am a] jury member who caused a hung jury. Two months later, evidence showed the guy was indeed not guilty. AMA."

Like many pages on Reddit, an AMA might look like a total mess to an outsider. The cascading, text-heavy site has a careful order, but it takes a moment to see the method behind the madness. So here's a beginner's guide to reading along and joining in on Reddit's Ask Me Anything interviews.

The format is simple enough. People post a message on Reddit's forums saying "I am a [blank]. Ask me anything." It's customary to provide some proof that people are who they say they are. Readers can then respond in one of two ways. Some will join in on the conversation, asking – or replying to – questions. Users also vote on which questions they find interesting. Popular comments rise to the top, making it easier for the interviewee and readers to follow along.

This democratic free-for-all allows the community to guide the conversation. Commenters may be as serious or as goofy as they like. The group decides what the group wants to know.

For example, Reddit asked Obama about space exploration (he's for it), his most difficult decision as president (sending additional troops into Afghanistan), and his favorite basketball star (Michael Jordan, "I'm a Bulls guy").

The president did not answer several of the most popular questions, such as his views on the "revolving door" of retired congressmen becoming lobbyists and whether he'd rather be attacked by one horse-sized duck or 100 duck-sized horses.

Obama answered 10 questions in his 30-minute interview, which disappointed Reddit fan Andy Mackenzie. AMA participants usually agree to two hours. Some of the most popular people return a day later to answer follow-ups.

Mr. Mackenzie, a graduate student in New York, says that first-time AMA readers may be thrown by Reddit's system of indentation. If you reply to a comment, the site tucks your message underneath the original. "On the far left, you've got the original question," he says. "Indented below that are direct responses and there can be many, many levels of indents" as side conversations play out.

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Visit reddit.com/r/iama for a current list of AMAs. There's also a partial schedule of upcoming interviews.

For more on how technology intersects daily life, follow Chris on Twitter @venturenaut.