Q: how do regular major/minor chords such as Cm FM Gm Dm differ from C7m F7M G7m etc?
A: the 7 is supposed to go after the m, otherwise it actually looks like it means something different, because of some quirks about the way 7's are used when writing chord symbols. but the 7 means there's another note you have to have. Cm7 includes Bb note, and so on. Cmaj7 includes B note, and so on. 'C7maj' is unfortunately not clear as to what it means and this is due to a quirk about what just C7 means (hint, it might not be which 7 you'd expect)