You say Service Desk, I say Help Desk: Don't call the whole thing off

Customer Support and Help Desks do happen to share a few functions: problem logging, problem assignment, problem escalation, problem tracking to resolution, problem trending, and a knowledge base for sharing the answers to problems.

Clearly, both of these departments work on problems.

However, it is most commonly accepted that a help desk is inward facing and used by internal staff. Customer Support is outwardly focused and used by people external to the business. Usually customers. (Makes sense)

For further differentiation, here is a list of functions generally found in help desks but not customer support:

Tracking configuration changes
Tracking IT inventory
Managing IT assets
Creating SLAs
Developing reports for various uses

Meanwhile, the customer support desk can be found doing these where the help desk generally doesn't:

Manage opportunities
Up selling or cross selling
Planning marketing activities
Dispatching field service
Implementing personalized customer experiences

Whew! I'm glad we got that out of the way. I hope you find it instructive. If anyone has anything to add, we'd like to hear it.