Although I work in the IT field, I am not in anyway claiming to be an expert. I can tell you in short, what your OS does in regard to a swap or page file.
A computer can only “work” on something in memory. When you are attempting to load more into memory than your system can handle, it swaps the program / data you are not using to the page file as pages (or chunks), and loads the program or file you are trying to work on. This is why, when we have eight programs running, you can hear the hard drive crunching as you switch back and forth between programs. You computer is dumping some of the data in memory to the hard drive… and pulling the stored data back into memory.
If you create a page file, but do not exceed your memory limitations… your OS “should not” use the page file. This is not an absolute… but in general it should apply
I would personally use one. If you need it, and it is not there, I have seen things get cranky
But then… I use SSDs