When washing rice you are supposed to wash the rice until the water is clear.
Washing or rinsing the rice until the water runs clear is a a common practice when preparing rice for cooking.
When you rinse or wash the rice until the water runs clear it helps remove any excess starch and debris from the rice, which results in the rice being fluffier and also less sticky when cooked.
Some people avoid rinsing the rice or washing the rice until the water is completely clear, but it's a common and recommended way of preparing rice for cooking.
When you do wash the rice until the water is clear it improves the final texture of the cooked rice.
I always wash my rice until the water runs clear and it really does make a difference.
However if you are cooking the rice for a dish that requires a stickier texture such as paella or risotto then you want to rinse the rice less thoroughly.
But for many other dishes or when just cooking rice to eat you should ideally wash the rice until the water is clear but it's okay if you don't do so.