Dumbel Vs Resistance bands? Is there a differance?

So I was wondering if there is a difference between working out/ weight lifting using weights vs Resistance bands? I have both, I have my 3lb set of girlie dumbells and the 40 lb set I bought my boyfriend which alternates from 2.5 to 20 lbs on each barbells. I also have a bally red resistance band I got from Avon in 2001 when I sold it. Ive used both and dont really understand if there is a difference or they are the same, just some people prefer either or?