The comparison of two numbers is called a proportion, sometimes a fraction.
For example,
2:5 is a proportion, meaning compare 2 with 5
2/5 is a fraction (that means divide two by five)
Since we use fractions a lot, and to make it convenient, we would multiply the fraction by a 100, and call the resulting number percent, abbreviated (%). ("cent" means 100 in Latin, which is the root of most European languages). So instead of the clumsy way of writing (or saying) 2/5, we would say (2/5)*100%=40% (forty percent).
In summary, whenever we compare a number to 100, is a ratio called percent.