Checked Twitter lately? If not, brace yourself for reams of breathless chatter about the sprawling southern "carnaval" known as South by Southwest (SXSW). Lasting until March 18, SXSW is a 10-day music, film, and interactive-technology festival that each year draws over 200,000 people — fans and journalists alike — to Austin, Texas. But what exactly is it, and what makes it so popular? Here, a brief guide:

What is SXSW?
It started in the late '80s as a local music festival, and has grown into a premiere launching point for up-and-coming music acts, under-the-radar movies, and burgeoning tech startups. Because of its cachet, the biggest names in entertainment and tech now flock to Austin each year as well. The film festival, for one, "boasts the most varied and never-ending line-up of the year," says Movieline, with low-budget documentaries and big studio releases like 21 Jump Street and the Joss Whedon-produced thriller Cabin in the Woods competing for buzz. On the music front, indie bands hoping for the big breaks intermingle with big-name acts such as Bruce Springsteen, the festival's keynote artist, and Jay-Z. Set for tech panels this year: Twitter, Skype, Facebook, and more.

Why is it so popular?
To begin with, its sheer size. SXSW showcases over 2,000 musical acts alone, according to its website, staging concerts at over 90 venues around Austin. "With a smorgasbord of new and rising bands in every genre," SXSW is "the most determinedly forward-thinking event around," says Eleanor Kagan at NPR. Fans have decent odds of feeling like they've "witnessed something significant," be it a new discovery or a veteran like Jay-Z. The festival lets tech aficionados get their hands on the newest technologies first. Products that launch at SXSW routinely become the "buzzwords that graduate to everyday vernacular," says Mat Honan at Gizmodo.

How successful is it?
It has the power to really launch products and people. Just last year, SXSW hosted the premiere of Bridesmaids, dispelling all doubts that the raunchy female comedy would get major buzz. The rest is Oscar-nominated history. Grammy-nominated act Foster the People, whose earworm "Pumped Up Kicks" proved practically inescapable in the latter half of 2012, broke out at last year's music festival. Other acts that arguably owe a great debt to SWSX: Amy Winehouse, The Strokes, The White Stripes, Spoon, and Bon Iver. On the tech side, there's Twitter and FourSquare. Without SXSW, says Honan, "you may never have even heard of them."

What's garnering buzz this year?
The Channing Tatum-Jonah Hill comedy 21 Jump Street is earning Bridesmaids-esque raves, while The Cabin in the Woods premiered to a "raucous, rapturous reception." HBO screened one of its upcoming TV shows, the Sex and the City meets twentysomething Brooklynites comedy Girls, at the festival, receiving buzz as "the most original, spot-on, no-missed-steps series in recent memory." The music acts expected to be big this year include "gospel-garage" band Alabama Shakes and indie rockers Howler, according to the U.K.'s Guardian. And the next great social media platform to come out of Austin: Highlight, an iPhone app that alerts users when they are physically near their friends.

Sources: Entertainment Weekly, Guardian, HLN, Hollywood Reporter, Movieline (2,3), NPR, Reuters, Spinner, SXSW, USA Today