I have heard and read that a picture can be better than a thousand words, that perhaps being the case, rather than me rambling on at length as I tend to do, perhaps if you beam up the data available from the link below you will find all sorts of info on understanding the operation of a starter motor and associated circuits...? If you get stuck on anything, plenty of help here to assist the learning process..?

https://www.youtube.com/results?search_query=ford+cvh+starter+motor+tests

Good luck.