Conflict 1. a struggle between opposing forces; battle. 2 opposition between ideas, interests, etc.; controversy. 3 Psychol. opposition between two simultaneous but incompatible wishes or drives, sometimes leading to emotional tension.
In real life, most people try to avoid conflict, but in fiction it's vitally important if the story is to progress and keep the readers interest. The need to overcome the conflict is often the focus of the hero. If nothing in the story forces the character to see something in a new light, to confront their worst fear or greatest personal challenges, then there is no conflict and no character growth.
Whether it be through internal conflict: guilt at cheating at a test or on a partner, a phobia etc., or external conflict: arguments, a fight, being pursued, being ditched at the altar, create conflict.