MI6 (Military Intelligence section 6) is the British Secret Intelligence Service often known by its initials, SIS with a remit to conduct espionage activities overseas, as opposed to the MI5 which is tasked with internal security within the United Kingdom.
MI6 (Military Intelligence) is the British Secret Intelligence Service. This British Secret Intelligence Service is often known by its initials to conduct espionage activities overseas. This was as opposed to the MI5. This MI5 is tasked with internal security within the United Kingdom. Its initials are SIS with a remit. Military Intelligence is 6.