12/33 as a percentage is 36.36%. This is the rounded value you get when you turn the fraction into a percent with two decimal places.
The fraction 12/33 can be simplified a little, but it already shows the relationship between the two numbers clearly. It tells you that for every 33 parts, 12 of them are being counted.
When you see 36.36% on a chart or a report, you can think of it as the same idea as 12 out of 33. It’s a handy way to compare that part to a whole that’s been divided into 100 pieces.
Knowing the percent version makes it easier to talk about the fraction in everyday situations, like grades, discounts, or statistics, where percentages are the norm.