Quest

Here you have many quests to choose from, you unlock more quests as your level gets higher.
Then they get harder and much bigger rewards.

Once you have choose the quest you want to do it will show a description of what you need to do in order to get the rewards.

As it tells you your requirements to completing the quest, you have a little button below this box, which will tell you have job in a better way of understanding.

As you can see once clicking this button it changes the way it looks.
This can explain a quest much better in understanding.

Here you can see your rewards which you will get for completing the quest you have on.

Once you have a quest accepted it will highlight in orange showing the ones you have active.
To cancel any of these just click on an orange one and click cancel.