What is a relative frequency distribution?

It's a frequency distribution in which all numbers are represented as a fraction or percentage of the complete sample size.

There is really no more to it. You add up all frequency-numbers to get a grand total = your sample size.

Then you divide every frequency number by your sample size to get a relative frequency fraction . Multiply this fraction by 100 to get a percentage . You may insert these percentages (or fractions) in a separate column after your frequency numbers.

Cumulative frequency
If you have ordered values, like test-scores on a scale from 1-10, you may want to use cumulative frequencies. They mean "everything up to and including this value".
Let's take the scores. In the row behind "1" you fill in the frequency number, behind "2" you add the numbers for "1"and "2" and so on.
Check! The last number should be same as your sample size!

After completing this column, you can easily answer questions like: how many student failed (score <"6")?

Cumulative relative frequency
You can convert the same way as from frequency to relative frequency. So now you have a colum saying how many percent (or what fraction) have scored up to and including a certain value.

It's now easy to do some statistics!
The value for which the cumulative relative frequency passes the 50% (or 0.5) mark is the median. Same goes for the 25% ( Q1 ) en 75% mark ( Q3 )