Golf balls don't last forever. They can get scuffed, damaged, split, cracked or otherwise disfigured -- and all of that can happen in the normal course of play. They can also simply run out of mojo, at least in the eyes of a golfer.
Fortunately, under the Rules of Golf, golfers are allowed to change golf balls at various points during a round.
Under normal conditions -- meaning the ball wasn't damaged beyond reasonable use, or it didn't wind up in a water hazard or was lost -- a golfer can change golf balls in between holes. Once a hole is completed, a golfer can swap out that golf ball for a new one before the start of the next hole. Generally speaking, however, a golfer is expected to play a hole with a single ball. This way, a golfer can't have a driving ball, an approach ball, a putting ball, etc.
There are four rules under the Rules of Golf which allow a player to substitute or change golf balls during a hole.
Rules 26-1 (Water Hazard Rule), 27-1 (Ball Lost or Out of Bounds) and 28 (Ball Unplayable) allow a player to replace a golf ball because it cannot be recovered or it cannot be played. In addition, Rule 5-3 permits a player to substitute another ball if the original ball has become unfit for play during the play of that hole -- that is, it was cracked, cut or otherwise rendered unusable.
When a golfer substitutes a golf ball, either in between holes or otherwise, they can replace that ball with any golf ball they have in their bag. It doesn't have to be the same manufacturer or even the same model of golf ball. However, there is the idea of the One Ball Rule, which is often used in competitions as a local condition of competition. A tournament organizer can require a golfer to use the same golf ball -- manufacturer and model -- throughout a stipulated tournament round. Failure to adhere to the One Ball Rule can mean a two-stroke penalty for each hole where the condition was violated, with a maximum of four penalty strokes.