When someone such as an actor or musician goes onstage, they go onto the stage in a theatre to give a performance. When she walked onstage she was given a standing ovation off-stage. on the stage in a theatre offstage
{s} located or occurring on a stage; pertaining to the part of a stage that is visible to the audience
situated or taking place on the area of a stage visible to the audience on the stage; "it was time for her to go onstage
onto the stage, onto the area of a theater where entertainers perform before the audience