It starts a counter at 0. It looks at the first sine value in the table. If that sine value is less than the calculated vale for our angle, then nothing happens. This goes on until our calculated value for our angle becomes LESS than the lookup value in the table. Than means the actual angle we are at is less than the one the counter is at.
Loops continue endlessly until the condition in the brackets is true.
This is just a fancy way to make the loop read more English-like. There is probably a more efficient way to make this whole code work. I'm certainly no programmer. But remember that the angle we calculated is between 0 and 90 degrees. Well, a full circle has 360 degrees.