At any point, you can see all of the assignments you have planned for upcoming days by looking at this list. Looking ahead allows you to plan, manage and prioritize your time better. 

If you wish to complete an assignment ahead of time, you can mark it as done by selecting the assignment and clicking on the button "I'm Done". By doing this, you will be redirected to Google Classroom where you can submit your work and the assignment in question will no longer appear in the upcoming list and will instead appear in your done list.