Understand the concepts of Interface Management

Interface management can seem to be very complex, and it is true that there are many different unique terms and expressions; the IT system tools are often not very intuitive; there are sometimes many different companies involved, and it DOES matter how the interfaces are structured. The amounts of money involved are eye-watering, and so are the losses if it goes badly...
BUT it all comes down to communication, people talking, and "making sure that nothing gets lost in the middle" between the contractors.

WHAT is interface Management?

WHY do we need to manage interfaces?

WHEN should we worry about interfaces?

HOW should we manage interfaces?