Percentage is a way of expressing a portion or proportion of a whole as a fraction of 100. It is denoted by the symbol "%". 



In simple terms, a percentage represents a number out of 100. It is often used to describe parts of a whole, compare relative values, or express changes or growth rates. 

To calculate a percentage, divide the portion or value being considered by the total and then multiply the result by 100. The formula for calculating a percentage is:

Percentage = (Part / Whole) * 100

For example, if there are 30 green marbles and 100 marbles in total, the percentage of green marbles would be:

Percentage of green marbles = (30 / 100) * 100 = 30%

Percentages are commonly used in various contexts such as finance, business, statistics, and everyday life. They are used to calculate discounts, analyze data, express probabilities, determine tax rates, measure growth or decline, and compare values relative to a whole.