The interpreter takes notes during the speaker’s presentation and translates afterwards.
Very long speeches may be broken up into parts, with interpretation after each part, or a dynamic sentence by sentence translation might be used, on the basis of a good working rapport between speaker and interpreter.
This kind of interpretation is suitable especially for very formal situations such as :
VIP press conferences.
And also for scientific and technical presentations given by a single speaker, or in meetings where only a small number of languages are spoken.