I've never really had the idea of progressivism defined for me, and I was only peripherally aware of it for a long time. Recently I became more exposed to it, and after reading articles and editorials by a number of progressive activists, I can say that there is a lot of overlap between progressivism and my own philosophy and beliefs.
I don't feel like I am enough of an expert to give a good definition of progressivism, but if you'd like to learn more about it, check out one of the links below. If nothing else, it's good food for thought.