The document defines fractions as numbers of the form p/q where p and q are whole numbers not equal to 0. Fractions represent parts of a whole, for example 3/6 of a pizza. The top number is the numerator and represents the number of parts, while the bottom number is the denominator and represents the total number of equal parts the whole was divided into. Calculations with fractions involve dividing the whole into the number of parts in the denominator and taking the number of parts indicated by the numerator. Whole numbers can be viewed as having a denominator of 1. Dividing by 0 is undefined in mathematics.