It is a term that refers to any business, department, or individual whose core output is a service or expertise rather than a manufactured product. A few examples of professional services include accounting, advertising and marketing, and legal services.

Professional services firms are profitable only when their team members bill hours to clients. Therefore, new work is often assigned to the person who's currently not working billable hours.

Professional services will use their product expertise to customize the technology to align with the customer's goals. They will then work with the customer to ensure the product's functionality is wholly understood and adopted company-wide.

With managed services, service is ongoing: as long as you're in business, you'll always need an IT help desk, so there's no clear endpoint for that line of service. Professional services tend to be time-limited and project-based, or at a minimum they're tied to a single event or initiative.