User Experience
The complete experience that the user has, from the time the problem arose in the customer's life which lead to them seeking out a product, right through to when they gave up attempting to use your ridiculous piece of software, sold their house and moved into an Amish community out of utter technological despair. That is User Experience.
My book "Choose Your First Product" is available now.
It gives you 4 easy steps to find and validate a humble product idea.