Slang for a nickname, pseudonym, alias or username. For example, a Twitter handle is how people identify themselves on Twitter. For decades, "CB handles" have been the short but unique identities truck drivers use over citizens' band radio (see CB radio
A temporary name or number assigned to a file, font or other object. For example, an operating system may assign a sequential number to each file that it opens as a way of identifying it.
In computer graphics, a tiny, square block on an image that can be grabbed for reshaping.
The handles are the tiny (blue) squares that are displayed when you select an object.