Suspense is holding your breath, waiting for the other shoe to drop. Take a second to picture that moment. Notice how your body tenses; you may clench your teeth or curl your toes up. Make a note for later.
Suspense is about heightened emotions. Do you want to have your reader breathless, stressed, intrigued, wondering what’s happening and what’s going to happen next? If you do, then you need to understand and utilize suspense.