Understand 'performative' as an action done through words, like making a promise. Saying 'I promise' is a performative act that commits you.
Pro Tip 2/3
Context Sensitive
Recognize that performative statements depend on context to be effective, like a wedding vow. The celebrant's 'I now pronounce you' is performative in context.
Pro Tip 3/3
Social Force
Know that performative language can have social power, initiating or changing relationships. Her declaration 'We're friends now' was a bonding performative.