A rate quote isn't one number
Every rate comes attached to a cost. The same loan might be 6.5% with no points, 6.25% if you pay one point, or 6.875% with the lender paying some of your closing costs. None of these is 'the rate' — they're points on a curve, and you choose where to sit on it.
What a point is
One point is 1% of the loan amount, paid at closing, in exchange for a lower rate. On a $400,000 loan that's $4,000. A lender credit is the same trade in reverse: you accept a slightly higher rate and the lender covers some of your costs.
The only question that matters
How long until the monthly savings pay back what the points cost? If a point costs $4,000 and saves $60 a month, that's about 67 months — roughly five and a half years. Staying longer than that, points win. Selling or refinancing sooner, they don't.
This is why 'what's your rate?' is an incomplete question. The honest answer is another question: how long do you plan to keep this loan?
Why quotes differ
Credit score, down payment, property type, occupancy, loan amount and lock period all move pricing. Two lenders quoting the same day can differ simply because they're assuming different points, or different lock lengths. Compare rate AND cost together, or you're not comparing anything.