You get your rating when you play against a person. You can see it in your profile.
Rating
There is a measure of deviation called the Rating Deviation. Once it gets under 30, it's probably close to being stable.

How many games played does it take for a rating to become somewhat relevant? Your opinions please.
I think its something like 20 games. around then it gives a pretty good indication of where you are at.

Yeah 20 games or so is about the point where rating doesn't fluctuate as crazily from game to game, but ideally the more games (bigger sample size) then the better.
Once you stabilize your rating range for the most part, then you can work on whatever you are lacking to reach the next range...same process even for chess Grandmasters. Of course, chess is just a hobby for most (including myself), but even hobbies can take a lot of effort and time investment if you want it too.
Have fun with your chess journey and feel free to chat, or ask questions, if you like
See ya around chess.com

Really stupid question here. How do I know my rating or how do I get a rating? I've only played one human online game here. Everything else has been vs computer. Thanks
See, it should take around 20-30 games to show your true rating.
Even if you sign up as higher rated than you are, your rating will drop as you will be beaten by those in the proper rating pools.
So yeah, 20-30 games
Yep. I'm 1-0 vs a human novice like me and show a rating over 900. Haha. So, playing 20-30 games in my weight class makes sense. I guess I'll find out what my weight class is! I'm assuming though that wins, losses, etc is only a factor of the the rating. Is that correct?

It took me between 30-50 games to stop hemorrhaging rating points and to start slowly climbing back up.
Edit: Actually, looking at my games it was more like 70 games before I started to climb again.
Thanks. One more question on ratings. Is this rating primarily a reference for playing on chess.com only? Or, is it meant to be a useful tool anywhere one might play? Hope that makes sense.

Thanks. One more question on ratings. Is this rating primarily a reference for playing on chess.com only? Or, is it meant to be a useful tool anywhere one might play? Hope that makes sense.
It can be a useful tool anywhere, but any rating is only as accurate as its "rating pool." chess.com ratings only align among all active chess.com players, FIDE ratings align with all FIDE players, USCF rating align with all USCF players and so on. This means that 1800 chess.com is not equal to 1800 USCF.
Typically speaking, ratings will only vary a few hundred points from another, but even from online site to another ratings can vary a lot.
chess.com is probably one of the most accurate sites to OTB (over-the-board) ratings because chess.com is the world's largest chess site, but even chess.com rapid probably is a few hundred points "weaker" than OTB organizations like FIDE or USCF.
It took me between 30-50 games to stop hemorrhaging rating points and to start slowly climbing back up.
Edit: Actually, looking at my games it was more like 70 games before I started to climb again.
This means that chess account rating cannot die! We can only hemorrhage to 100 points at worst and then chess blood will be restored once again.

It can be a useful tool anywhere, but any rating is only as accurate as its "rating pool." chess.com ratings only align among all active chess.com players, FIDE ratings align with all FIDE players, USCF rating align with all USCF players and so on. This means that 1800 chess.com is not equal to 1800 USCF.
Just a small, subtle clarification to KeSetoKaiba's excellent post: These rating systems generally work somewhat similarly and try to do the same thing, but in general you cannot directly compare results from one site to another, both because of the rating pool difference but also because the average numerical score of that rating pool differs depending on choices about how the system is managed.
Also, the systemic details are different enough between each site (or governing body) that even the very same series of games would get you different scores that wouldn't necessarily correspond.
If you're interested in how this washes out in practice, this article compares how ratings correspond between Chess.com, Lichess, USCF, and FIDE.
Really stupid question here. How do I know my rating or how do I get a rating? I've only played one human online game here. Everything else has been vs computer. Thanks