I’ve done some research about the Apollo 11, and I don’t really understand what happens with different kinds of pre launch tests. For example, what are first-stage propellant tanking tests? And also, what are the names of the other pre-launch tests? What do they do? This is for a National History Day project.
In general, the prelaunch tests make sure that all of the systems on the rocket work as designed, before you get to the launch.
The pre-launch tests are the last stage of testing. Every part of the rocket is checked and tested during manufacture and assembly, checking e.g. if the correct materials have been used and making sure there are no defects. When a subassembly is ready, it's tested again, to check if the parts work together. When a bunch of subassemblies have been assembled into a stage, it's tested again to see if the stage as a whole works.
Your example, the first-stage propellant tanking test: the first stage is placed on the launch platform (this is the first time it'll be on the platform), and you try to fill the propellant tanks (as you would before a launch). All the parts involved have been tested before, but it's the first time the complete chain from fuel tanks to stage is tested.