System scope and context - as the name suggests - delimits your system (i.e. your scope) from all its communication partners (neighboring systems and users, i.e. the context of your system). It thereby specifies the external interfaces.
If necessary, differentiate the business context (domain specific inputs and outputs) from the technical context (channels, protocols, hardware).
The domain interfaces and technical interfaces to communication partners are among your system’s most critical aspects. Make sure that you completely understand them.