When you visit a website that supports @anywhere, you'll be able to follow any Twitter account associated with that site without navigating away to the profile at Twitter.com. The Twitter blog suggests that the platform will let you follow a participating journalist from his or her byline. It also suggests that you'll be able to tweet about a YouTube video without interrupting it.
More @anywhere features are planned; Twitter says the above-mentioned items are are "just the beginning." Integrating with the rest of the web is a wise move. Facebook's Facebook Connect platform is dominating right now, and while Twitter has a similar login platform, it's lost its head start when it comes to openness and integration.
The person or organization behind a website can drop some JavaScript in the website to integrate with @anywhere, so there won't be any arcane Application Programming Interface (API) to learn and implement. Initial partners will include Amazon, AdAge, Bing, Citysearch, Digg, eBay, The Huffington Post, Meebo, MSNBC.com, The New York Times, Salesforce.com, Yahoo, and — as mentioned above — YouTube. Twitter hasn't said when those sites will begin using @anywhere.