Why does irrational numbers don't stop?
Because if they stopped they could be expressed as a ratio.
Suppose the decimal expansion of an irrational stopped after x digit AFTER the decimal point.
Now consider the number n, which is the original number, left and right of the decimal, but without the decimal point. This is the nummerator of your ratio. The denominator is 1 followed by x zeros. It is easy to show that this ratio repesents the decimal expansion of the number
Yes, any positive number is a number that doesn't have a (-) behind it (-20; -23.67; -45.45454...), and is not zero (0). Any repeating number (see 3rd negative example) is irrational, no matter what its sign. Irrational numbers also include numbers (decimals, specifically) that don't repeat, but don't stop. Numbers that don't terminate include pi. Pi, as it is, is proof of a positive irrational number.