$\frac{1}{3}$

The top number is the numerator.
It represents the number of parts that are selected.

The bottom number is the denominator.
It represents the number of parts the whole is divided into.

A model can be used to represent a fraction.
The model can be a whole divided into equal parts, or a number line with equally-spaced tick marks between whole numbers.

The models below represent $\frac{1}{3}$. Each whole is divided into three equal parts, and one part is selected or shaded.

	grid model	fraction circle model
fraction strip model

A group of objects can also be used to represent a fraction.
Out of the 4 nests below, 3 of the nests have eggs.
So, $\frac{3}{4}$ of the nests have eggs.

A whole must be divided into equal parts to represent a fraction. The model below does not represent $\frac{1}{3}$ because it is not divided into equal parts.