There are two types of tasks. Main story tasks that advance through the main story of the game and secondary tasks that give extra rewards by completing certain objectives, such as upgrading the hospital or staff members to a certain level. The task button shows the requirements and the reward you will get from completing it. Secondary tasks may require you to wait for a timer, the timer can be bypassed using gems. Gems can be obtained through playing or in the shop. Tasks can be accessed by clicking on the tasks button in both hospital and merging scenes.