Complex sentence: The Foley artist on a film crew is the person who creates and records many of the natural, everyday sound effects in a film, in contrast to the production of special (audio) effects, which is generally left to the sound designer.
Split into simpler sentences: The Foley artist on a film crew is the person who creates and records many of the sound effects. Specifically, the Foley artist typically has the job of capturing the natural/everyday sounds, leaving the role of special (audio) effects to the sound designer.