Flash CS5 is part of Adobe's Creative Suite released on 30 April 2010. Its main features over its predecessors are the iPhone packager, new text engine (TLF), and code snippets.
About Flash:
Flash is a multimedia platform used to add animation, video, and interactivity to web pages. Flash is frequently used for advertisements and games. More recently, it has been positioned as a tool for "Rich Internet Applications" ("RIAs").