An executed contract is when all parties have fulfilled their promises.
For example, a sales contract is complete when the transaction closes. The buyer has paid the money, and the seller has transferred the title.
Do not confuse an executed contract with the act of signing a document. People often make the mistake of thinking a purchase contract is executed when everybody signs and have come to an agreement. That just means it is executory.
An executory contract is when one or both parties have obligations still to be performed.
For example, a sales contract is an executory contract until the buyer has obtained financing—there are still obligations remaining to be performed before the contract can be considered executed.