At the most basic level, the user interface (UI) is the series of screens, pages, and visual elements—like buttons and icons—that enable a person to interact with a product or service.

User experience (UX), on the other hand, is the internal experience that a person has as they interact with every aspect of a company’s products and services.

What is UI?
Simply put, user interface (UI) is anything a user may interact with to use a digital product or service. This includes everything from screens and touchscreens, keyboards, sounds, and even lights. To understand the evolution of UI, however, it’s helpful to learn a bit more about its history and how it has evolved into best practices and a profession.

As with any growing technology, the UI designer’s role has evolved as systems, preferences, expectations, and accessibility has demanded more and more from devices. Now UI designers work not just on computer interfaces, but mobile phones, augmented and virtual reality, and even “invisible” or screenless interfaces (also referred to as zero UI) like voice, gesture, and light.

Today’s UI designer has nearly limitless opportunities to work on websites, mobile apps, wearable technology, and smart home devices, just to name a few. As long as computers continue to be a part of daily life, there will be the need to make the interfaces that enable users of all ages, backgrounds, and technical experience can effectively use.

What is UX?
User experience, or UX, evolved as a result of the improvements to UI. Once there was something for users to interact with, their experience - whether positive, negative, or neutral - changed how users felt about those interactions.

Cognitive scientist Don Norman is credited with coining the term, “user experience” back in the early 1990’s when he worked at Apple and defines it as follows: "'User experience’ encompasses all aspects of the end-user’s interaction with the company, its services, and its products."

That’s a broad definition that could encompass every possible interaction a person could have with a product or service - not just a digital experience. Some UX professionals have opted for calling the field customer experience, and others have gone a step further to simply refer to the field as experience design. No matter what it’s called, Norman’s original definition of UX is at the core of every thought experience design - it’s all-encompassing and always centered around the human being it's interacting with.

The foundation for best practices for UX professionals to help guide their efforts across multiple touchpoints with the user include:

• How they would discover your company’s product
• The sequence of actions they take as they interact with the interface
• The thoughts and feelings that arise as they try to accomplish their task
• The impressions they take away from the interaction as a whole

UX designers are responsible for ensuring that the company delivers a product or service that meets the needs of the customer and allows them to seamlessly achieve their desired outcome. UX designers work closely with UI designers, UX researchers, marketers, and product teams to understand their users through research and experimentation. They use the insights gained to continually iterate and improve experiences, based on both quantitative and qualitative user research.

What's the difference between UI and UX?
At the most basic level, UI is made up of all the elements that enable someone to interact with a product or service. UX, on the other hand, is what the individual interacting with that product or service takes away from the entire experience.

UX is focused on the user’s journey to solve a problem, UI is focused on how a product’s surfaces look and function.

"UX design is focused on anything that affects the user’s journey to solve that problem, positive or negative, both on-screen and off. UI design is focused on how the product’s surfaces look and function. The user interface is only piece of that journey. I like the restaurant analogy I’ve heard others use: UI is the table, chair, plate, glass, and utensils. UX is everything from the food, to the service, parking, lighting and music.” (Ken Norton – Partner at Google Ventures)

"A UX designer is concerned with the conceptual aspects of the design process, leaving the UI designer to focus on the more tangible elements.” (Andy Budd)

“I think one of the most important things to keep in mind in our artificially - intelligent world we’re flying headlong into, is that UI is no longer just a series of buttons relegated to the four corners of a screen - and UX is not just a screen-based prototype meant to increase conversions on a landing page.

It can also now be considered our voice and intentions powered by whatever the machines think we’re saying or wanting in any given context. UI is the bridge that gets us to the other side of where we’re wanting to go. UX is the feeling we get when we get there when the bridge is well-built, or plummet to our death (talk about bad UX!). Keep in mind that we’re always creating UX, all the time whether behind a keyboard, in the grocery store line or in our workplace." (Jason Ogle)