A fraction is a representation of a rational number written with two numbers separated by a slash. Like: 1/2. Or one over the other, separated by a horizontal line. Thus:
The top number is called the numerator. The bottom number is the denominator.
All fractions can be expressed as decimals, and vice versa. If the denominator is not a power of ten, you get a repeating decimal or repeating fraction. You can round it off, or use a vertical line over the repeating digits.
1/3 = 0.33 (rounded to two digts)
The digit 3 repeats indefinitely, so if you need more precision you can write 0.33333 or whatever.