"Difference" is a noun, while "different" is an adjective. By the way, I hope you don't mind me correcting this but it's a very common error in English learners: your question should be "What do difference and different mean?". The pattern is "What does X mean?" and not "what's mean X" or (very common error) "what means X". If you wanted to be even more clever you could have asked: — Why are "difference" and "different" different? or — What's the difference between "difference" and "different"? :-)

When you meet two different people you might ask "what is the difference between them?" Well they are of different genders, different heights, weights etc. Works for all things as welll. , so give me two different cities, Paris and London. Why are they different? Well the differences are size, language etc.