Chess ratings represent the relative playing strength of a player; in a game between two rated players, the player with the higher rating is more likely to win. How much more likely depends on the difference in ratings.
For example, if one player is rated 100 points higher than the other, the lower rated player will likely only win 1 in 3 games. However, if the difference is 400 points, the lower rated player will likely only win 1 in 10.
To provide a sense of scale, a beginner might have a rating of about 500, whereas a Grandmaster typically have ratings of at least 2500 (The top human players in the world have ratings around 2800). An average "club level" player, which is someone that plays very regularly, might be rated about 1500.
The calculator here will give you an idea of the expected results for a given rating difference.