Twitter API

Twitter exposes its data via an Application Programming Interface (API). These documents are the official reference for that functionality. The Twitter API consists of three parts: two REST APIs and a Streaming API. The two distinct REST APIs are entirely due to history. Summize, Inc. was originally an independent company that provided search capability for Twitter data. Summize was later acquired and rebranded as Twitter Search. Rebranding the site was easy, fully integrating Twitter Search and its API into the Twitter codebase is more difficult. It is in our pipeline to unify the APIs, but until resources allow the REST API and Search API will remain as separate entities. The Streaming API is distinct from the two REST APIs as Streaming supports long-lived connections on a different architecture. The Twitter REST API methods allow developers to access core Twitter data. This includes update timelines, status data, and user information. The Search API methods give developers methods to interact with Twitter Search and trends data. The concern for developers given this separation is the effects on rate limiting and output format. The Streaming API provides near real-time high-volume access to Tweets in sampled and filtered form.
More information: http://dev.twitter.com/