MEL
(Maya Embedded Language)
MEL is a programming language like C that can be used to make doing anything in Maya easier, or even automatic.
Like any language it has a proper syntax and a set of predefined commands. You can use these commands to make more complex commands and tailor them to your own workflow. A common use for MEL is in the expression editor. You'll find this handy tool under Window>Animation Editors>Expression Editor. It looks like this:
Lets try using this editor in a new Maya scene.
Another convenient use for MEL is in the Hotkey Editor. You can bring up the interface for writing you own Hotkeys by using the menu: Window>Settings/Preferences>Hotkey Editor.
The most powerful and unrestricted use for MEL is in the Script Editor. You'll find it here: Window>General Editors>Script Editor.
While the Script Editor is a great way to test and keep handy bits of MEL code around, nothing beats the security and versatility of MEL stored in global procedures. They can be created and edited in any text editing software and easily shared from one computer to another. The easiest way to describe global procedures is to say that they are scripts with names.
Lastly, here's some information you may find helpful as you begin to write your own scripts: