Infinity is big. Zero is not. There are two subdivisions of the real numbers. They are either rational or irrational. The set of integers lies within the set of rational numbers.
Integers are just positive or negative whole numbers.
A number line is a tool for students of math to help them visualize numbers. It is simply a horizontal line with vertical markings that represent numbers. When adding numbers, you can use a number line to count. Some numbers cannot be represented as a fraction with integer numerators and denominators. These numbers are called irrational numbers.