Script nodes are a way of storing a MEL script in a Maya scene file.

You can set a script node to execute its “payload” in response to various events:

• When the node is read from a file.
• Before or after rendering a frame.
• Before or after rendering an animation.
• When a file is closed or de-referenced.

A script node has three attributes: Before, After, and Type. Depending on the Type of script, the Before and After attributes specify when the script executes.