Pretend you're at a cocktail party. As is usual, you're milling about, meeting people and exchanging the standard "So, what do you do" lines. To some people, your answer of "I'm a user experience designer" makes sense - they're in the web/tech world as well and are familiar with they type of work. However, occasionally, the conversation goes as follows:
Innocent partygoer: "So, what do you do?"
You: "I'm a user experience designer"