A real number includes all the numbers existing in mathematics. Be it a negative integer or a positive one, a zero or a non zero number, a fraction, a decimal, a rational number or an irrational number - ANYTHING. It just has to be a number. All the numbers come under the category of real numbers. However, complex numbers are not just real numbers. They consist of both a real number and an imaginary number.
Following are some examples of real numbers -
0, 1.75, 13/17 , 1/3 , 3/10, 4, 5 etc. Any number, all the numbers, belong to this category - the category of real numbers.