For years, the usual way to start applications was to open a menu and click ones way through submenus, or to click on starters on the desktop or on the panel.
Gradually, some desktop environments added alternatives for users relying on the keyboard. Gnome Shell allows users to type the applications name, as does Unity.
Xfce users are not provided with anything like that by standard, but it is easy to add without having to drag a whole new desktop environment on the system.
kupfer is (not only) a launcher that makes starting programs a matter of a mere instant. Activate the launcher, type the program's name (or even only a part of it; to start Chromium I simply press c) and hit enter - that's it. Simple and quick.
Several plugins even allow you to search stuff at Wikipedia, control Audacious, open files, write Emails, switch between windows and workspaces ... it would take to much time and space to list all.
I implicitly recommend this software.