Percent means out of one hundred. It is often shown with the symbol "%". It is used even if there are not a hundred items. The number is then scaled so it can be compared to one hundred.
For example, I have a bowl of fruit with three apples and one orange. The percentage of apples is 3 out of 4 = 3/4 = 75/100 = 75%.
A percentage is one way of writing a ratio; you can also write it as a fraction or decimal. There are ways to convert fractions to percentages or decimals to percentages.