Percentages measure the frequency of occurrence of a certain event with respect to the occurrence of another event.
This is measured as a division or ratio:
The basketball player made 76 out of 100 attempts. Here, our event 1 is the basketball player making a free throw. Event 2 is the player throwing the ball, regardless of its result.
Since he/she made 76 out of 100, the percent is:
The percent is 0.76*100 = 76%