Requestor checks your answers and evaluates your skill — your ability to complete a certain task type. Skills are evaluated on a scale from 0 to 100 points. You can view your skill level on the profile page.
Skills help the requestor to give the tasks to the people who can do them well. The more skills you have and the higher they are rated, the more tasks are available to you.
If you do certiain types of tasks poorly you will get a low skill level. Over time, you may stop receiving such tasks.