Pacing is a lot like the throttle on a vehicle. There are times when driving that you need to move slowly, like through a city or in a school zone. Then there are times when you need to move a lot faster, like on the freeway. And there are times when you need to just coast along at a moderate speed.
The pacing in your novel is a writer’s tool to help you manage the speed and rhythm of your story. Sometimes you want fast action, just as other times, you need to slow things down and let the scene unfold.
It’s up to you to know when to use pacing. A lot of your pacing decisions will be based on your genre. If you’re writing an action story, it’s pretty fast-paced with exhilarating moments of danger mixed with adventure juxtaposed with quieter moments when your characters do some heavy thinking. If you’re writing an epic that spans over generations, it might move more slowly.