Final answer:
Line Number is the feature that shows the line number your cursor is on in a programming environment, aiding in debugging based on compiler error messages.
Step-by-step explanation:
The feature that shows you what line number your cursor is on, which is useful when a compiler gives error messages with a line number, is referred to as the Line Number.
It is commonly found in various programming environments and text editors used for coding. For example, in the Arduino programming environment, this feature is typically displayed on the left-hand side of the Sketch Editor, allowing developers to quickly find and correct errors highlighted by the compiler.