Everything on browsers is rendered on pages, everything on apps is displayed on screens. Pages and screens are navigated through links. Frameworks like Ionic and React Native can be used to render pages on mobile apps. We used to create content on desktop applications using forms and some people still do but majority now use pages and screens. Pages are fancy.
Forms are used to collect data on the web, when you sign up on TikTok, you’re filling a form. Buttons are used to submit forms. Buttons can also be used to make pages more interactive and perform other actions including navigating pages and screens. Pages are edited using markup languages. HTML, XML and XAML are examples of markup languages. Stylesheets are used to style pages. Some platforms and people use markup languages to style pages. Screens are like pages; you can program them with XML and also with backend languages like Java or Swift.
The most popular scripting language is JavaScript. Scripts can be used to make animations, validate forms, display or hide contents on pages. Scripts can also be used to do logic. The other very popular scripting language is Typescript. Typescript is less forgiving than Javascript and requires strict adherence to its rules. There’s been massive improvements to JavaScript over the years, frameworks have been built on JavaScript. One of the most powerful ones is NodeJs, NodeJs can be used to develop JavaScript outside pages, NodeJs can be used to develop APIs.
There are two ways I think of APIs, internal-facing and external-facing. Internal facing APIs are used by organizations to create, store, retrieve and update data. When you login with your username on this app, the screen is using an internal-facing API to validate your credentials. If you login with another account e.g. Google, X is using an external-facing API to validate your credentials.
Pages and screens use APIs to communicate with Databases.