The term "snap" has multiple meanings, depending on its context.
1) It can refer to a brief or sudden action, as in "He took a snap decision." This usage implies that the action was quick and spontaneous.
2) In photography, it refers to the sound made by a camera's shutter when it opens and closes to take a picture.
3) It can also refer to an electronic message or communication, as in "I sent him a snap." This usage implies that the message was brief or concise.