you can imagine this as a venn diagram. the "or" event would consist of everything in both sides and the middle of the venn diagram because you can choose form either event x or event y.
the "and" event would consist of everything in the middle of the venn diagram because you choice must be a part of both event x and event y.
the complement of an event is just everything that is not included in the event. for example, in a coin flip, the complement of heads is tails. in a dice roll, the complement of {1,2} is {3,4,5,6}
so if you come across these just think "either or" or "both and." and remember that the complement is everything excluding what is listed.
i apologize if this does not help, im not that great at explaining things