A microchip can be used to identify a pet's owner when a dog or cat is found and brought to a veterinarian. A GPS tracker tracks the location of your pet in real-time, enabling you to always know where your pet is and to find them immediately in the case that they run off, preventing them from getting lost in the first place.
Most microchips are the size of a grain of rice, allowing them to be implanted under the skin. A GPS tracker is a bit larger at 35 grams, as it contains a battery pack, GPS antenna, GSM module, etc. which are necessary for tracking your pet. It can be easily attached to your pet's collar.
Read more about the differences between microchips and GPS trackers in the Tractive blog.