There are two types of quests: Main line and side quests.
Once a quest is completed, you will move on to the next one.
Quests include upgrading buildings, defeating NPCs, obtaining equipment, collecting quest items, etc.
Click on the green keywords in the guide to activate quest navigation, automatically switch to quest interfaces and display arrows pointing to quest objectives. The reward screen will automatically open upon quest completion.
Completing quests will also reward large amounts of resources or EXP.