First off would be to find websites that describe the parts in a stock engine. Generally they are all the same, just designed differently and shaped differently.
Once you know the parts on the stock engine, all these parts are just different variations on those.
There are some animated pictures on youtube that show an engine being assembled from the ground up, and then shows how it works.
btw, a cam is the spinny thing that hits the pokey things that make the rocking things push the pancake things which leads to suck squeeze bang blow out the stinky things.