In simultaneous interpretation, the interpreter interprets for an audience in another (the target) language while the presenter speaks normally without pausing.  The presenter speaks to the interpreter or through an earpiece.  

SimultaneousSimultaneous interpretation is a challenging task that requires not only knowledge of both languages and subject matter, but also the ability to listen. The interpreter cannot start interpreting until he understands the meaning of the sentence so he will start giving the interpretation of a finished sentence, while simultaneously listening to and understanding the speaker’s next sentence. Hence, the complexity of the task and mastery of the subject matter involved requires a specialized interpreter. Not every professional interpreter is trained and skilled to be a simultaneous interpreter.
Simultaneous interpretation is a good fit for multilingual conferences and training sessions. It’s widely used in scenarios where different interpreters have to translate many languages at once. Example: UN meetings.
These events are usually lengthy. It is difficult for the interpreter to sustain the mental effort for a long period of time, so usually, interpreters work in pairs to divide the workload.
The use of equipment such as headphones and microphones is common for simultaneous interpretation, and technicians are often involved in such events.