A fraction is a number that is not a whole number where the top number is called the numerator and the bottom is called the denominator.
Examples of fractions

The shaded part of the rectangle are shown as a fraction underneath the rectangles.
Mixed numbers and and improper fractions
You can also have fractions which are bigger than 1.
Examples
11/2 or 3/2, 10/4 or 22/4
These are all examples of mixed numbers and and improper fractions.
There are 2 halves in a whole so the improper fraction for one and a half is 3/2.
The mixed number fraction is obviously 11/2.
Equivalent Fractions
Equivalent fractions are found by cancelling or multiplying the numerator and denominator by the same number.