One of the most powerful use cases of Teams is any cross-organisational processes, where multiple departments communicate seamlessly on related matters regardless of location, a project is typical place where this would take place.
A team is designed to bring together a group of people that work closely to get things done. Teams can be dynamic for project-based work (for example, launching a product), as well as ongoing, to reflect the internal structure of your organisation (for example, departments and office locations). Conversations, files and notes across team channels are only visible to members of the team.