"Portal" is a magic trick performed by the illusionist David Copperfield, in which he takes a member of the audience and transports both of them to a pre-selected location (Hawaii, The Hoover Dam, Australia), before reappearing on stage.
The effect of the illusion is a disappearance of the magician and an apparently randomly-selected audience member, and their reappearance in the pre-selected location via video feed. After the reunion of the audience member and a loved one, Copperfield then appears back in the audience on the other side of the stage.
The disappearance is considered the most effective part of the trick, as it involves two adults apparently vanishing into thin air from a raised platform above the audience's heads.