UI means user interface: the parts someone uses to interact with a system. UX means user experience: the broader experience of using it, including whether the task makes sense and can be completed. UI contributes to UX; the two are not simply “looks” and “works.”
Compare them in a form
The field labels, controls, focus indicators and status messages are interface decisions. Whether the person understands the request, trusts it, can recover from an error and gets the promised result belongs to the broader experience.
A form can look polished while asking for information it does not need. A clear workflow can still fail if its controls have poor contrast or cannot be used with a keyboard.
Ask different questions
For UI, inspect names, hierarchy, spacing, focus and visible states. For UX, observe the whole task: what brought the person here, where they hesitate and what happens after submission. Avoid assuming a visual preference tells you whether the task was successful.
Exercise: ask someone to find and use an example on a lesson page. Record the path and difficulties without coaching. Then identify which issues concern the control’s presentation and which concern the flow or explanation.
Read UI, UX and usability testing for distinct next steps.
Sources
Reference 1 Reference 2 provide the technical details and current compatibility information.