The fraction 37/91 works out to about 40.66% when you change it into a percent. It’s a simple way to see how big that part is compared to a whole.
Since 37 out of 91 pieces are taken, the fraction shows a little less than half of the whole. In decimal form it is roughly 0.4066, which is the same as the percentage above.
Knowing the percent makes it easy to compare with other numbers, like test scores or discounts. It tells you quickly that 37/91 is just under 41 out of every 100.