Numismatics is simply the study of coins and paper money, more generally, coin collecting. If I won a lottery it's a hobby I would return to, but it isn't really one that can be pursued on a student budget if one's particular interest is in hammered (pre-machine made) British coins in very fine condition. It's much more affordable if your interest is in collecting a penny from each year since 1937, but my interest was tied to an interest in British history. At one point I had a silver penny from the time of William the Conqueror, and it was like owning a bit of that history.
I suppose I'm continuing this interest in archaeology, though the need to actually 'possess' a piece of history has diminished. I'd much rather collect replicas. You get much nicer pieces ( the British Museum would love to sell you the Rosetta Stone in either regular size, or small).
Here are some links if you're interested in checking out this 'king of hobbies and hobby of kings'.