Constatives and Performatives are two different parts of speech. Constatives are sentences that describe something as true or false and Performatives are sentences that denote an action.
Performatives act upon the world.
Speech Acts are words that are themselves actions. These include ordering, promising, apologising, warning, sentencing, christening, marrying.
Performatives depend on context and reception. These are known as Felicity Conditions.
Felicity Conditions are the rules under which the performative can be enacted.
The Performative should be authoritative, clear, understood, and it should be able to be executed.
If it doesn't meet these conditions it doesn't have the power to denote action. But it doesn't mean that it is implicity followed.