There was a difference once upon a time; they're interchangeable now. Here's a Wiki: Drawing from that:
The Wrecking Crew: << Trailer for a delightful documentary
Funk Brothers: << We wouldn't have Motown without them
Nashville A-Team: << They helped shap Country music
Muscle Shoals Rhythm Section: << a 15 minute snippet from a film
The Section: << No vid available Note: This is NOT the Section Quartet--another group entirely.
Here's an interesting piece on session musicians and how the craft has changed: