discount points or buying points

[Darling N.]

Can someone please explain to me how buying points work? Will buying 1 point decrease my interest rate by 0.25? Because I have lenders telling me it won't, but my research contradicts that. 

Do different lenders apply points differently? Like lender A will reduce my rate by 0.25 then lender B might only reduce the rate 0.125? 

Thanks in advance, I hope I made sense.