Cancelled Members - how does it work?

2 questions please:

1) How does someone "cancel" their subscription? I can see options for update or downgrade but not cancel. How can this be processed?

2) When a member cancels their subscription, what 'role' do they get demoted to? Is this automatically subscriber level? OR do I need to set this somewhere? The "stranger" settings are set to a member role called "site visitor", which is attached to subscriber. Is this the role that it uses for this?

Cant get my head around this bit so any support would be great.