Interpretation or interpreting is the facilitating of oral or sign-language communication, either simultaneously or consecutively, between users of different languages. Translation studies is the systematic study of the theory, description and application of interpretation and translation.
An interpreter is a person who converts a thought or expression in a source language into an expression with a comparable meaning in a target language either simultaneously in "real time" or consecutively when the speaker pauses after completing one or two sentences.
The interpreter's function is to convey every semantic element as well as tone and register and every intention and feeling of the message that the source-language speaker is directing to target-language recipients (except in summary interpretation, used sometimes in conferences)
For written speeches and lectures, sometimes the reading of pre-translated texts is used. (Source: Wikipedia)