The Hoyarex seem to be special effects filters except for the skylight. The sepia is used to give an antique(ish) effect with color film and the PL linear is a polarizing filter that allows you to reduce reflections, increase saturation with some subjects. It's not hard to use and if you look through it and rotate the filter you should see a change in most subjects. It will not reduce reflection from chrome or mirrors but works well on reflections from glass. It will also deepen the blue sky. but not at all angles.
The Cokin 80 a and c are color correction used with color films under tungsten light. The orange and yellow are used to increase contrast with black & white film and the dreams is a special effect filter.