A course rating of 74.8, for example, means that scratch golfers are expected to post an average score of 74.8 from that set of tees on that course.
A course rating of 74.8 is pretty stiff, but there are no hard-and-fast parameters for how high or low course rating can go. Most course ratings range from the upper 60s to the mid 70s.
Golf courses that participate in the USGA Handicap System are rated for each set of tees at their course (front tees, middle tees and back tees, for example). Most have separate ratings for some of their tees for women golfers. For example, the forward tees might be rated 67.5 for men and 71.5 for women.
Course ratings play a key role in determining a golfer's handicap index in the USGA Handicap System. However, course ratings have also been adopted in many places that are not governed by the USGA.