rehearsal -
a practice session in preparation for a public performance (as of a play or speech or concert); "he missed too many rehearsals"; "a rehearsal will be held the day before the wedding"
rehearsal -
The practicing of something which is to be performed before an audience, usually to test or improve the interaction between several participating people, or to allow technical adjustments with respect to staging to be done.
Wikipedia
A rehearsal is a preparatory event in music and theatre (and in other contexts) that is performed before the official public performance, as a form of practice, and to ensure that all details of the performance are adequately prepared and coordinated for professional presentation.