Pre-qualification (sometimes called "pre-qual") is what a broker does in a 15-minute phone call — rough scenario review, ballpark rate and payment, directional answer on whether the loan closes. No credit pull, no document review. Not binding on the lender.
Pre-approval is a conditional commitment: the lender has pulled credit, reviewed income docs and assets, and issued a letter saying "we'll lend up to $X for a property meeting these criteria." Most California purchase offers require pre-approval to be taken seriously.
Important distinction for listing agents: a pre-approval from a broker or lender they respect carries weight. A pre-qual does not. If you're competing on a property, ask your broker for a full pre-approval before you write an offer.