Pick

From GuitarWiki

A pick, (also called a plectrum) is a small piece of shaped material that is held in the pick hand and used to pluck or strum the strings of the guitar. Picks are typically made out of vinyl or plastic, but some are also made of glass, metal, and stone. Some players have even been known to use metal coins as picks.

picking

To pick, is to use a pick/plectrum to pluck the string and make a sound with the guitar. See Picking and Plucking.