If you are ever considering going pro, here is some useful information. Phil Mickelson, four time major winner, has a handicap index of +5.2. Here are some of his scores from Whisper Rock, a course he is a member at.
A very good golfer would have a low digit handicap such as 3,2, or 1. A scratch handicap would be a 0. Almost all touring pros will have a handicap with a + in front. Supposedly at one point in time, Tiger Woods was a +10.