A fraction is a part of a whole.

A fraction has got two numbers.
The top number is called the numerator.
The bottom number is called the denominator.

Annie:
Annie received 1 slice.
So, her share of the pizza was

1

4

.
The numerator, which is 1, tells us how many slices Annie got.
The denominator, which is 4, tells us how many equal slices the pizza was cut into.

Betty:
Betty received 2 slices of the pizza.
Betty's share of the pizza was

2

4

.

2

4

can be simplified to

1

2

.
So, Betty's share of the pizza was

2

4

or

1

2

.

Charlie:
Charlie received 1 out of the 4 slices that the pizza was cut into.
Charlie's share of the pizza was

1

4

.