It is a technique (in a cabin and with earphones) in which interpreting is performed at the same moment in which the speaker emits the message.
The interpreter orally translates (interprets) the messages of the speaker while he/she speaks and the audience listens to the interpreter in real time using specific earphones.
This type of interpreting provides the best result in terms of quality, immediacy and fluency and is a technique commonly used in conference situations like conventions, seminars, meetings or exhibitions when there is a large number of participants.