Fiddling around today I discovered if you type on the desktop version of raspbian without selecting a window it shows up in a window in the upper right. It doesn't seem to do anything other than sit there, is this a bug or just not fully implemented?
In LXDE, your desktop is managed by PCManFM, which is also LXDE's file manager. PCManFM has a function to find items in a folder by typing the first letters of it. For example if you type
apple, it'll spring to the first item that start with
apple. Since PIXEL is just a fork of LXDE, it has that feature too.