This is our unofficial GML FAQ.
What is GML?
GML is the scripting language of Game Maker.
What does GML mean?
GML stands for "Game Maker Language".
What's a scripting language?
A scripting language is a light-weight programming language created to control the features and functions of a pre-made application of game.
Do I have to learn GML to make a game?
No. You can make a perfectly noob game without it.
Do I have to learn GML to make a good game?
Is GML an OO Language?
No. GML is a procedural scripting language. It appears to be object oriented to novice programmers because the scripting language is mostly used to control game objects.
Can I make my own functions in GML?
No — at least not in the traditional sense. If you need to create your own functions, the best you can do is create a script and call it from a game object.