Game Maker Language
From YoYoGames Wiki
Game Maker Language (GML) is a scripting programming language developed for use with a computer game creation application called Game Maker. It was originally created by Mark Overmars to supplement the drag-and-drop action system used in Game Maker. However, in the latest versions, all the drag-and-drop actions are based on GML rather than being separate from it.
Many of Game Maker's features are accessible through the drag-and-drop interface, but GML extends the functionality by providing functions that are not usable through the drag-and-drop interface, such as file handling functions, online multiplayer functions and functions to call external DLLs.
In Game Maker, GML is used in conjunction with drag-and-drop. Unless the entire project is written in GML, scripts cannot be called without drag-and-drop actions, but all drag-and-drop actions may also be written in GML. Most projects consist of both GML and drag-and-drop actions, depending on the programmer's preferences.