What's the difference between UI Design and UX Design?

UX = User experience, how the user feels when using the website, how easy it is to use

UI = User interface, it's how the user see the components on the screen

UX :

User experience, its how the end-user see the web-site, deal with componant the experience of how easy the user can use the site

UI:

User interface, its a collection of components designed to make the web site

• UX design deals with the overall experience associated with the use of a product or service.
• UI design deals with the specific user interface(s) of a product or service. The UI can be a component of UX, but many user experiences don't have UIs. The design of a UI will be heavily informed by the UX design. The UX design will be less informed by the UI.

As most peopel have stated, UX is the overall experience the user has when interacting with the site or application. The UI only plays one role in this experience and that is to present the data whether image or text or other in a specific way.

The UX design process starts way before UI design process and UX design needs to feed into UI design. UI design relies on the research and decisions  which come out of the UX process to implement specific UI approaches as solutions.

The UX process does not end one UI has been implemented, it is a cycle and needs to be repeated to re-evaluate the user's experience and incrementally improve the entire system and thereby the user's overall experience of thr system.

As most peoples already mention UI = User interface is about what your site structure and design where UX = User experience is about flow of your design and how user feel during browsing website  its may include Navigation placement to the way you present elements 

UI is user experience, it include the sturcture / design of website.

UX is user experience, it include how you can make your website easier to use for your visitors.

UI: A User Interface is:

• A tool
• A Point of Interaction
• A means of communication between person and system 

UX: User Experience:

• Is the interaction itself
• Includes interfaces
• Addresses all aspects of a thing as perceived by a person

in UI, web designers, create their own website design, with the components to their creativity and client requirements ,while in UX, Web designers create a website design and components, and invite profiled users, who are potential kind of users to do usability testing, and give their impression about the the Usability of the website, with the web designer and developer present to monitor the Users reaction, without having that affect his creativity in his web design work, But the Users feedback on it is  priority, example users can give  a feedback about the website that the font is too small, or too colorful, ot the design is to tech savy, upon this feedback the Web designer amends the web design according to Usability first.

UI != UX

   I think that UI refers to the aggregation of approaches and elements that allow the user (s) to interact with the system or solution. But UX is considered as the reactor of the brand, it's an intellectual asset in my think.  brand being, in essence, the sum of the experiences that a person has with a company or organization. User experience is the goal.

UX : how to make the user experience easy and useful

UI : User interface, it's a collection of components designed to make visual interface

UI and UX are interlinked. UI is the face of any program, idea. UI gives it look and feel that connects the product with a user with easy to understand and smoothly running interface, and UX provides a logic behind it.