EvoX is the name of hacked BIOS (the other commonly used BIOS is called Xecuter). Evolution-X is a dashboard.
Dashboard is the program which is being loaded every time you start your Xbox. Original Microsoft Dashboard allows you to run original game DVDs, play audio CDs, change settings and manage saves. When you have a modchip installed, you may run any application as dashboard. 'Alternative' dashes such as: Evolution-X, Avalaunch or UnleashX, give you the ability to create menus with games/apps/emulators on your HD, play MP3s in background, change very specific settings (like video region), download RSS feeds from Internet and more... They're all fully skinable. You may also use Xbox Media Center directly as a dashboard. Personally, I use old Evolution-X as a my primary dashboard, with ability to launch Microsoft Dashboard, XBMC and UnleashX any time from Evolution-X main menu.
There is a sample screenshot of Evolution-X root menu: http://www2.uk-dave.com/projects/xbo...hot-dash-2.jpg