Macromedia Flash Player is free software that lets you view web content created by Macromedia Flash. This content may be interactive content such as menus that slide, or may be complex programs like games and movies. Some web browsers install Macromedia Flash Player automatically, but you may need to upgrade it from time to time as Macromedia makes improvements and as websites you visit update their content.
NOTE: If you don’t want it, make sure you don’t install Yahoo! Messenger along with Flash Player 🙂