A star on a map is typically used to represent a capital or a major city. A circled dot may also be use in place of a star. Stars are primarily found on political maps and might not appear on a physical or contour map.
1 Additional Answer
In most cases if you look on a map and see a star it would indicate the capital of a state or country. You may also notice a star on a map that is giving you directions, the star would indicate the location you are trying to find.