Numbers are those integers used in a certain equation. For example: 5, 10, 5/4, 11, .1542, -100; these are all numbers despite its differences, may it be negative or positive number, may it fraction or decimals.
Variables refer to the letters used in a certain equation. For example, 5x, x is the variable used. This is usually used to represents unknown numbers.
And lastly operation and symbols, Operations are used to add, subtract, divide and multiply the given equation. Symbols are used to get the square root of a given number and more.