I somehow missed this news earlier that Twitter acquired Vine around October last year. Apparently Jack Dorsey liked the Vine demo so much that he pushed for Twitter execs to acquire near-launch Vine.
Since the acquisition last year, the team Vine has been polishing their app and integrating it with Twitter for native display. Just the other day Vine iPhone app has just hit the market.
The concept is really simple. Vine lets you record video snippets up to 6 seconds, and share it with other users. It acts and feels much like GIF animation in that it loops the video, but different from it in that it adds sounds.
Twitter community is starting to debate whether this is a good move for Twitter. Some are concerned that adding video will complicate Twitter UX and cause Twitter to lose one of its key asset, simplicity. Some believe that it is a brilliant move that readies Twitter for upcoming IPO (I don't think there is much disagreement in inevitability of its IPO).