chess points

It is really quite complicated. In general if you win you should gain points and if you lose you should lose points. If you win, the points you get will be more if the rating of the player is higher. Conversely, if you lose, the points you lose will be more if the rating of the player is lower. However, when you first start playing on chess.com there is a large uncertainty about your rating. Because of this, the points change can be quite large. Overtime it settles down, as the uncertainty of your rating reduces; this then means that the points change becomes smaller and smaller. Sometimes, if you beat someone who is much lower rated than you or with a similar rating it may be that your rating does not go up at all (for example, it might internally go from 800.1 to 800.2 but these scores will both round as 800 so it will look like no change). 

It is worth saying that some games are unrated. If a game is unrated then no matter what the result there will be no effect on your rating. Also, in a rated system if someone resigns after one move there will be no effect on your rating even if you win.