Since the 10.4 version OS X has had a search system called Spotlight. Among other things, Spotlight allows you to search your computer for files matching whatever criteria you enter. In addition to regular files, Spotlight will also show you any programs that match what you’ve typed in. In 10.5 or newer, the tip hit will also be highlighted first and you can simply press enter to select it.
You can access Spotlight in two ways, by click its icon () or pressing command+spacebar. Start typing the name of the application you want launch and press enter when it is highlighted.
This will launch the application. Over time you’ll find you can search for and launch applications very quickly using this method.