Each rating is it's own little microcosm. Instead of something objective like how high you can jump, ratings only compare you to others in the same pool. On chess.com you might be 700 blitz, but on a different site you might be 1000 (or 500, or -30 or a million). On chess.com ratings like puzzles and lessons and daily chess tend to be higher than ratings like rapid, blitz, and bullet. That's not because one type is harder than another it's just how it is.
(The guy who came up with the rating system originally suggested people set 1500 as the average, and as an artifact of that today we have ratings that resemble that, however on one website I've seen they start players at zero, and a very strong player might be rated 500)
Anyway, so to answer your question, if someone (who is a chess player) asks me how good I am, I'd give them something specific like #### USCF, or #### chess.com blitz. If someone tells you they're rated 1300, it's a reasonable question to ask them to elaborate ("which website? What time control?")
Depending upon the type of play, I have a range of scores that go from 500 to 1000. Would the best way to understand my skill level be to find the average of these scores?