Interpreting percentile ranks

A percentile is a measure used to indicate the percentage of observations that fall below a value. 

For example, if you scored at the 95th percentile on a test, then about 95% of the students who took the test scored below you and about 5% of the students scored above you.

For example, if you are at the 20th percentile of the heights of students in your classroom, then about 20% of the students in your class are shorter than you and about 80% of the students in the class are taller than you.