What is a "task"?

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I am new to Mylot and I am wondering if somebody can please take the time to tell me what is a task. I have no idea what they are and when I click on tasks Mylot says that their are none that are available for me to do? Do you need to be a user for a certain amount of time or have a certain rating before you can do them? Also, I would like to know how much money one could realistically make doing them and how many times in one day can you do them.