The idea of a "sponsor" is almost exclusively an AA idea. The newcomer to AA is encouraged to "get a sponsor", that is, to find someone with significant experience in AA and sufficient length of sobriety to be credible, who will guide the newcomer through AA's 12 Steps and make certain that he or she stays the course.
Members of AA are encouraged to call their sponsors when they experience the urge to drink, or even when they are confused or discouraged.
In practice, sponsorship seems to many, even within AA, to be of questionable value; over-zealous or insensitive sponsors can drive a person away, and the sponsor himself may experience a good deal of emotional upheaval if one of the persons he is sponsoring drops out of the program and goes back to drinking.
Sponsorship is a relatively late addition to the AA program; there is no mention of it in the early editions of the Big Book. And it has not been adopted by other recovery programs, even by those that follow AA's lead in other regards.