wow man, that's a pretty big question. I would strongly suggest to start with Bitcoin, as it's the first, and in my opinion the only relevant crypto currency out there.

Have a look at this video by Andreas Antonopoulos, a very smart and long term prominent spokesman for bitcoin and crypto in general.

If you get hooked, and i am pretty sure you will :) i suggest to just keep watching his videos on his channel, he explains things very thoroughly at the beginner level.

Enjoy, and get ready to get your mind blown :)