ratings v actual skill level
they reflect so much that players with similar rating as yours will give you a competitive game and somewhat balanced game, other than that it reflects pretty much nothing
Well, if you play enough games, all the factors should even out.
Cheaters lower you, people who abandon for some reason raise you, people who start with a too low rating estimate lower you, people who start with too high rating estimate raise you, etc.
And everyone around you experiences the same, thus, again, it should even out after enough games.