### Theory:

Integers are the set of positive and negative numbers and zero. Even whole numbers are integers. Usually for better understanding integers are represented in a number line. Negative numbers will be on the left side of the number line, and positive numbers will be on the right side of  the number line.
Example:
The examples of negative integers are $$-1, -2, -2199$$.

The examples of positive integers are $$1, 38, 48, 122$$.

The number $$0$$ is neither negative nor positive.
Negative numbers are always lesser than zero and positive numbers.
$\begin{array}{l}1\right)\phantom{\rule{0.147em}{0ex}}-3<0\\ 2\right)\phantom{\rule{0.147em}{0ex}}-311<0\\ 3\right)\phantom{\rule{0.147em}{0ex}}210>-51000\\ 4\right)\phantom{\rule{0.147em}{0ex}}-200<500\end{array}$

Reflection of a number:
Reflection of a number will have the same absolute value as that number but with a different sign.
Example:
Reflection of $$-1$$ is $$-(-1) = +1$$
Reflection of $$20$$ is $$-20$$
The distance between the positive number and zero in a number line will be equal to the distance between the reflection of the same negative number and zero.
Example:
Let us take a number $$+1$$ its distance in the number line from $$0$$ is $$1$$.
Reflection of $$+1$$ will be $$-(1)$$ and its distance in the number line from $$0$$ is also $$1$$.
Distance between $$-20$$ and $$0$$ is $$20 =$$ Distance between $$20$$ and $$0$$.

Important!
Numbers with decimals $$(0.21, 2.35)$$, Irrational numbers $$π≈3.14$$, $$square$$ $$roots - √2,√3$$ are not integers.