The Lean UX Denver theme combines Lean and UX. Lean is centred on preserving the value of a product or service, while reducing the amount of work done by either the producer or consumer. UX or User Experience is about the methods to create a product with high Satisfaction, Efficiency, and Effectiveness for the user.
Lean UX'ers considers the expenditure of resources for any goal other than the creation of value for the end customer to be wasteful, and thus a target for elimination. For example putting an obstacle in the way of the user would be wasteful, but it would be also wasteful to make the user do something too hard. Lean UX'ers also try to reduce the amount of work to produce something, by identifying wasteful process, and bureaucracies.