When you role-play, you pretend to be in a situation that is not happening for real, so you can practise what you would say and do. Language teachers love it: one student is the waiter, the other is the customer, and you try the English you would need in a café. Offices and counselling rooms use it too — a job interview, a complaint, a hard talk with a parent — because it is safer to get it wrong while everyone knows it is only pretend. It is not a play for an audience, though actually the two sit close together; the point here is practice, not a show. You will hear it as a noun (a role-play) and as a verb (let’s role-play that call). Some people write roleplay as one word, some as two; the hyphen is the usual dictionary form.