The document discusses properties of rational numbers. It defines a rational number as a number that can be expressed as p/q where p and q are integers and q is not equal to 0. It then lists properties of rational numbers under addition: 1) closure, 2) commutativity, 3) associativity, 4) existence of an additive identity element (0), and 5) existence of additive inverses. Examples are provided to illustrate each property.