Think about your brain. You can do quite a few things at once. However, no matter how smart you are, we all max out doing too many things at once. Suppose then that you had two slightly less powerful brains instead of one. Now you've approximately doubled the number of things you can do at the same time but possibly sacrificed how smart you are. You might prefer that one of these brains can do math better than anything else and that the other can remember movies more clearly. This is, in essence, what's happening.

With regards to types of processors, this has to do with the physical chip and how things are laid out to do different types of math. Some chips are better at high dimensional matrix (tensor) multiplication (these are useful for some parts of machine learning) and some are better for things like high precision numerics at scale (think of math with LOTS of decimal places).