Labels may only exist in program memory; they make no sense in Run Mode. A label begins with the "@" sign, followed by between 1 and 16 characters, which may be any combination of letters, numbers, and the underscore character.  Unlike variable names, program memory labels can 'begin' with a digit (after the @ symbol, of course). Labels are essentially case-insensitive, as variable names are: upon exiting Edit Mode (whether to Run Mode or Help Mode), every lowercase letter in every label (and variable name) is replaced with its uppercase.

Labels are used for GOTO, GOSUB, ON ... GOTO, ON ... GOSUB, RESTORE, BGMSETD, and LIST commands.