Depressons/cyclone And Connection With Rain Or Snow.

[Crocodile23]

Hi, first post here, i've searched about an answer of that here, but i haven't found anything, sorry if my search proves to be flawed.

First what is the difference between the terms: "cyclone", depression" and "low system"?

Does all 3 mean the same thing? Or there are differences? If it's the latter then what these differences are?

Second and more important, i know for my area that when a low system(or cyclone or depression) approaches us from our west(we have sea in our west-i live in Thessaloniki-northern Greece) then it brings heavy rain phenomena or snow if temperatures et al, are appropriate.

But why? Why the low brings these precipitations? Does it needs to travel through sea to do it, or the mechanism has nothing to do with traveling through sea? If instead a low comes from our north(where there is no sea in its path), will it bring precipitations also?

So what i'm asking is what is the EXACT mechanisms that a low system brings precipitations? I have heard something about colliding with warmer pressure systems and then doing some procedures, but i can't find anything concrete.

Thanks.