Quran parts in Quran Life are not just labels. They define your current territory.
When you choose an active part, the app uses that decision to focus your daily portion, your todo flow, your statistics, and your maintenance work. That keeps the system from feeling like one giant undifferentiated Quran-wide checklist.
The normal progression is usually to begin with a part you already learned, so you can stabilize your workflow on familiar ground. After that, you move gradually into parts you have not yet learned, one territory at a time, until eventually the whole Quran is learned and you can switch to the all-Quran mode.
So a part is not just an organizational label. It is the answer to a practical question: what section of Quran am I actively trying to keep moving right now, without drowning the rest of the system?