What types of troops were used in western Europe during period and what were their functions (I understand this might be quite complicated but even a general answer would be helpful)?
As far as I can find the armies were made up of archers/crossbowmen, men at arms and knights. Were Men at arms used as the standard infantry? I'm also seeing references to more basic infantry (pike/billmen) but I can't find where they fit into everything else. Of course I'm not a historian so if I'm way off please correct me.
Sigh .... I am quite sure the reason this question has not received any answers yet is because you appear to be asking for a thorough overview of Medieval / Early Modern fighting techniques, which are a big subject. Add to this the lack of indication of how much you are willing to invest in learning.
So allow me to instead recommend a very easy to read book for you, Fighting Techniques of the Medieval World by Bennett, Bradbury, DeVries, Dickie, Jestice. I like their book series and they are highly accessible.
Cheers.