If we stop halfway between 0 and 1, we call that number a half - 1/2 - one out of two parts of a whole number. If we stop halfway between 0 and 1/2, we call that number a quarter - 1/4 - one out of four parts of a whole number. If we stop halfway between 2 and 3, we call that number 2 1/2. Or we can call it 5/2 - five halves, instead of 2 1/2 whole numbers. Or we could call it 10/4 - ten quarters of a whole number.
Another way to write the numbers that come between whole numbers is as decimals.
How do you add fractions together? If the denominators are the same, it's easy: just add the top numbers (the numerators) together: 1/8 + 2/8 = 3/8. But what about if the denominators aren't the same? Then you need to find a common denominator, make the denominators the same, and then add the numerators together. One way to find a common denominator is to multiply the denominators together. So to add 1/4 and 1/3, you find that 12 is a common denominator for them. Convert 1/4 to 3/12 and 1/3 to 4/12, and then add 3/12 + 4/12 = 7/12.