A number that has a decimal that does not repeat or end in an irrational number. The decimal goes on forever, without a pattern. Think of it as it is irrational to keep going on and on and on. Irrational numbers also cannot be put into fractions.
-5 is an integer, it is a whole (positive or negative without a decimal/fraction) number. An integer can be any whole number as long as it is a whole number and does not have a decimal.