Which types of quests are there in the game?

There are two types of quests in the game: main quests and side quests. You can find them in the Abbys' Journal. To open the journal, tap the icon with a notebook on it in the lower left corner of the game screen.
You will need stars to complete main quest. This will help you to upgrade the environment and progress through the story. You can earn stars by playing match-3 levels.
To complete the side quests you need to gather some items on the location. After the quest is complete, there is a chance you get a useful reward.