What's the main difference between the non-uniform probabilistic polynomial-time adversary and the probabilistic polynomial-time adversary?

Question

When I am reading some secure computing papers, the authors always assumed that there exist some adversaries, such as non-uniform adversary and the probabilistic polynomial-time adversary. So my question is that what are the main difference between the non-uniform probabilistic polynomial-time adversary and the probabilistic polynomial-time adversary ?