Notice of Termination of Agreement of Sale

The standard forms library has three(ish) forms that can be used to end a contract. Three forms that, despite the similar outcome, cannot be used interchangeably. But when do you use each of these forms?

A breach of the agreement by one party may justify termination by the other, even though the agreement does not specifically spell this out.

A Notice of Termination is unilateral. That is, the execution by one party is sufficient to terminate the Agreement of Sale. Why? Because the Agreement of Sale granted the right to that one party.