Can someone explain to me how the rating is calculated? Does a higher number of games lead to a higher rating, or does losing significantly decrease it?

Here's where you can find the formulas for calculating the rating: /topic/at/429696/.
And here's a discussion about the system I use to calculate the rating: /topic/5625/.
The change in your rating depends heavily on the current rating of your opponent. If you win against a player ranked higher than you, your rating increases significantly. If you win against a lower-ranked player, the increase is small. If you lose to a higher-ranked player, your rating doesn't drop much; but if you lose to someone lower-ranked, the deduction is greater.
You can view tables at /topic/3521/.
At the top of each season, there's a line that says "Results for each player are here." Click on "here" and analyze how much everyone gained or lost and why...