Generally a par 72 with a rating of 72 means that for a scratch golfer (0 handicap) the course plays to its par.

But if the course is a par 72 but has a rating of 69, it means that if a scratch golfer shoots level par 72, he effectively played 3 over his handicap. As 69 is really “par” for that course because it plays easier than the 72 on the scorecard suggests.

Same as if the par is 72 but the rating is 75, it means the course is 3 shots tougher than the par suggests.

Slope applies to a similar rating for bogey golfers (instead of scratch), read more here:

http://www.leaderboard.com/abcs.htm

So if you like to play “easier courses” choose courses with ratings well below their par. Conve!
rsely if you like to play tough courses, choose courses with ratings well above their par.