Use labels to give symbolic names to addresses of instructions or data. The most common form are code labels, which can be used—as the operands of call, branch, and jump instructions—to transfer program control to a new instruction. Also common are data labels that label data-storage areas.
label [: | ::] [directive | instruction]
The label field starts at the leftmost position of the line, with no preceding spaces. The colon after the label is optional; if it is present, the assembler immediately defines the label as a code label or data label. Some directives, such as EQU, require that you do not place a colon after the label.
This defines ExitPt as a code label for the RET instruction.
A label followed by a double colon makes the label public.