What is the HUD?
The HUD or Heads Up Display is a search-based alternative to traditional menus and is a brand new feature in Ubuntu 12.04 LTS.
Some apps likeor have hundreds of menu items. If you're using apps like these, you may remember the name of a menu option, but you might not remember how to find it in the menus.
Using a search box can be quite a bit easier and even faster than navigating complicated heirarchies of menus. The HUD also can be more accessible than normal menus as some people are unable to precisely control a mouse pointer.
Use the HUD
It's easy to try the HUD:
Tap Alt to open the HUD.
When you see a result that you want to run, use the up and down keys to select the result, then press Enter, or just click your desired search result.
If you change your mind and want to exit the HUD, simply type Alt again or Esc. You can also click anywhere outside the HUD to close the HUD.
The HUD keeps track of your search history and adjusts the search results to be even more useful the more you use it.