UI stands for “user interface”. Designers create UIs, UI designer jobs are advertised, people say they “do UX/UI”. It’s thrown around like everyone knows exactly what it means, but I’m not so sure.
An interface is a place. In Northern Ireland we have places called community interfaces. There is a point in space where my phone charger interfaces with the wall socket. A user interface on a computer is a place too; it’s where you or your organisation meets the people who have a reason to visit your website or app. Therefore it must be a place they’re comfortable visiting.
So a UI isn’t a collection of components or a set of interactions. It’s definitely not a picture of a web page! It’s a place, so treat it like one.