User rating is based on the overall evaluation of your answer quality during the whole time of using Toloka. If you complete tasks carefully and give answers according to guidelines your rating is going to grow.
The higher the rating is the more tasks are available for you.
Rating is an important indicator for requestors. They are interested in quality of answers and can set higher payment for users with high rating.
You can track the rating on the profile page:
Absolute rating reflects the quality of your answers. Make sure that it does not go down with time.
Relative rating is your place among all Toloka users rated by answer quality.