30.00% is what you get when you turn the fraction 24/80 into a percentage.
The fraction 24/80 can be simplified by dividing both numbers by 8, which gives 3/10. That means the part you have is three‑tenths of the whole.
Seeing it as a percentage makes it easy to compare with other numbers. Whether you’re looking at a test score, a discount, or a statistic, knowing that 24/80 equals 30.00% helps you understand the size of the portion at a glance.