Communications is roughly equivalent to the aggregate of marketing strategy, messaging, and PR but is also a form of context-signaling. The context is non-private sectors, such as nonprofits, higher education, NGOs. government, and especially politics.
It often means exactly the same thing as content marketing and brand messaging but signals more purportedly pristine motives than turning a profit. Meanwhile, Strategic Communications is a military and Fortune 500 concept that purports total control over all forms of messaging.