A good score in golf is typically anything under par. This means that if you are playing a course with a par of 72, a good score would be anything 72 or below. Of course, this can vary depending on the difficulty of the course and your own personal skill level. If you are just starting out, shooting for anything under 100 is considered to be pretty good. Once you get more experience under your belt, aiming for a score in the 80s is usually achievable. And if you're really looking to impress, breaking 70 is considered to be excellent.
Of course, there are always going to be those rare occasions when someone shoots an amazing round and goes way beyond what's considered good. But for the most part, sticking to par is a solid goal to strive for when hitting the links.