The original speach is immediately interpreted into the target language; the interpreter talks at the same time as the speaker, usually in a conference or meeting. For this type of interpreting, a pair of interpreters will take turns as the work is very demanding. Special interpreting equipment is necessary (radio microphone for the interpreter and headsets for the listeners).
The interpretation should be ordered at least 1-2 weeks in advance and you need to send supporting materials : the agenda, speakers´ addresses / contributions, etc.
You need to provide the interpreting equipment. I can give you advice on this.
This type of interpretation requires two interpreters. You or I can provide the other interpreter, as agreed.