A play is an agreed upon set of actions the team takes in a given situation.Having a playbook of commonly used tactics lets team members understand their role in executing each play.
A playbook has three attributes: (1) it gives you plays that can be reliably repeated, (2) these plays can be taught to others, and (3) one can look back and check whether the plays were used as intended.
Plays are not requirements, but are suggestions. They suggest what worked well in the past.
Plays do not guarantee advancement to the next stage. Sometimes they will give you exactly the confirmation you need to move on, other times you will have to go for a second round or for another play altogether. That's OK.