UX - User Experience, sometimes linked to the term human-centred design. How and why people interact with products. UX can be applied to most things from website navigation to building new products. UX is not to be confused with UI - User Interface design. The primary focus of UX is not how a website looks, rather it's about how a website works and how users use it.
Building a website: Asking why before determining how.
When marketing to audiences their actions are often assumed, however we know where assumptions can lead us... Understanding UX can help us substantiate or dismiss these assumptions. By creating an effortless experience for customers when they interact within various channels, you can create a less stressful and less conscious user experience. This helps establish an effortless and delightful experience with your product or service.
I've written a piece about human-centred design on my blog that digs a little deeper into what the principles of UX are and why this thinking is extremely relevant to us as marketers.
Some great books on the topic: