system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what is the difference between British intelligence MI5 and MI6?

is there only MI5 and MI6? why no other numbers?
gpt
Mi5 is the domestic intelligence service. They focus on counter terrorism and intelligence within the UK. 

Mi6 is the foreign intelligence service. They focus on overseas intelligence to support the UK’s national security.