The buttons the customer pushes, the place they scan their apple pay or insert money, all the ways the user interacts and experiences the vending machine is your frontend.

Also all the images printed on the front of the vending machines and the fancy graphics and fonts, graphic design, is all part of the frontend.

There's a lot you can do today with AI. But, you'll still probably want that expert human touch. Think of AI as just a set of amazing tools your human designer and human frontend engineer can use to do their jobs well.

Common frontend tech is react and react native. Also html, css, javascript and typescript. But with mobile apps the frontend can be in Apple's iOS SwiftUI or Android's Jetpack Compose.