Did you know that your golf handicap may be different from course to course? If you use the USGA system, this is true. The USGA provides a formula with which you first can calculate a number that is the same no matter what course you play. This number is called the "Index." Using this Index, you can calculate a second number - your golf "course handicap" - for any specific course. The USGA has a handy golf course handicap calculator so you don't have to do the calculation. But you will have to know your Index in order to use it. Alternatively, you can use the following formula to calculate your course handicap:
Course Handicap = Handicap Index x Slope Rating / 113
The course handicap is really a handicap for a specific set of tees on a specific course or what someone might call a "playing handicap."
The USGA defines a course handicap in its Handicap Manual as...
A "Course Handicap" is the USGA's mark that indicates the number of handicap strokes a player receives from a specific set of tees at the course being played to adjust the player's scoring ability to the level of scratch or zero-handicap golf. For a player with a plus Course Handicap, it is the number of handicap strokes a player gives to adjust the player's scoring ability to the level of scratch or zero-handicap golf. A Course Handicap is determined by applying the player's Handicap Index to a Course Handicap Table or Course Handicap Formula. (See Section 10-4.) A player's Course Handicap is expressed as a whole number. The result of any conditions of the competition, handicap allowance, or competition from a different USGA Course Rating that changes a Course Handicap is considered to be the Course Handicap.
So you have a course handicap that is specific to a set of tees at a certain course as well as an Index that is the same number from course to course. An approved golf club can provide you with a USGA Index which you need in order to calculate your course handicap.