The document defines and provides examples of conditional statements, converses, and biconditionals ("if and only if" or "iff" statements). It explains that a biconditional combines a conditional statement with its converse, making the statement true in both directions. Examples show biconditionals used to define mathematical and geometric relationships, such as a number being divisible by 5 iff it ends in 0 or 5. Definitions are also explained to be reversible, and can thus be written as biconditionals.