What do the "Percentile" and "Glicko RD" on my Stats page mean?

The title says it, pretty much. Not very important, just curious.

Percentile is how you compare to all the other players on the site. eg. If your percentile is 99% you are rated in the top 1% in that format (blitz, bullet, daily etc). Glicko is how accurate your rating is, based on how many games you have played. The lower the glicko, the more accurate your rating. Thus when you first join your glicko is high and you can win and lose 100's of points for each win and loss, but if you have played 1000 games your rating is firmly established, your glicko is low, and you get only a few points swing either way.

Yes you might be right there jonathan, that would also make sense. Possibly a combination of both number of games and frequency I'm not sure.

Yes the calculation of Glicko Rd is based in part on the number of games played over a specified time span ("rating period").  See the section titled "The Formulas" on page 2 of the following:

http://www.glicko.net/glicko/glicko.pdf

In particular note the last sentence in the first paragraph of that section:

"The length of time for a rating period is at the discretion of the administrator."

"Rating period" is used to determine the number of games that will be be used in the calculation of Rd, and therefore rating and rating adjustments.  From what I have been able to gather, chess.com does not publish what it considers to be the "rating period".  A shorter rating period generally implies fewer games typically played during the rating period, which would (all else being equal) result in a larger Rd being computed and employed in the rating calculation. 

A concern I have is that I believe the "rating period" for correspondence (i.e., chess.com "daily") chess should be longer than for shorter time controls (live, bullet, blitz, rapid, etc), because of course, daily chess games take longer to complete than live chess games, thus fewer daily chess games are typically completed (on average) over any given time span.  If the same rating period is used for both daily and for live chess formats, and assuming (plausibly) this would typically mean that fewer games would be used in the Rd calculation for the daily chess rating calculation, then the computed Rd for the daily chess rating will be larger than for the live chess rating.

http://www.glicko.net/ratings/rating.system.pdf

https://www.chess.com/forum/view/general/does-glicko-rating-system-work-well-with-cc

https://www.chess.com/forum/view/general/chess-rating-system

Thanks a lot guys for taking the time to answer. RussBell, thanks for sharing that link, it was rather interesting. 

Welcome!