Mopar engine differences

The more I learn about mopar topics, the more I learn there are more topics to learn about. So as I talk to people, research different things, I come across people saying "short block", "long block", "big block", and "small block". This may be all semantics or they might all be a real thing. Can someone either explain the differences, or if it is too long of a discussion, can you point me to a site that can explain it all? Thanks.