This is a whole circle.

Here is the circle divided into $2$ equal parts.

Each part is called a half. The whole circle is made of two halves.

This picture shows one half colored blue.

The number one half looks like this. $$\frac{1}{2}$$

The $2$ on bottom means $2$ equal parts. The $1$ on top means $1$ of those parts. So, $\frac{1}{2}$ of the circle is colored blue.

Here is a rectangle.

This picture shows one half of the rectangle colored blue.

What fraction do you think would describe the blue part of this rectangle?

There are $3$ parts so the fraction has a $3$ on the bottom. One of the parts is blue, so the fraction has a $1$ on top. The fraction is $$\frac{1}{3}$$ It is called one third.

The fraction $\frac{2}{3}$ would look like a rectangle cut into $3$ parts and $2$ of the parts are colored blue. Here is a rectangle that is two thirds colored blue.

Here are pictures that show fourths of a circle.

One fourth.

Two fourths.

Three fourths.

Four fourths.