charecter motivation, helps the story move forward. Charecter motivation is the reason behind a charecters ehavior and decisions. It's just like how we need motivation our selves to do a task. Charecter motivation helps the plot progress, and also gives reasoning. For example, in a story, a charecter may go on a quest to get revenge for his brothers death. The motivation of the charecter is the brothers death, which in return grows the plot of the story, while also progressing said story forward.
I hope this helps in some way shape or form.