The 1PPS signal can be very valuable. The pulse will normaly occur at the “top” of the second with a certain amount of jitter. Often the jitter is measured in the nanoseconds but for some units this might be a handful of microseconds. If you are trying to get multiple computers at remote locations to do something at the exact same time, then you can use the PPS signal to synchronise them. You can also use the PPS to get a highly accurace RTC since the GPS PPS will not drift over time. Each pulse may have some jitter, but over years, the PPS will be dead on.
PS: Do not confuse PPS (Precision Positioning System) with pulse per second.