A play is an agreed upon set of actions the team takes in a given situation. When you say "Daily Stand-Up" everyone knows what that means and knows what they need to do to execute that play. Having a playbook of commonly used tactics lets team members understand their role in executing each play.
Plays are not requirements, they are suggestions. They merely 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.