Front-end developers develop for...

A front-end developer typically uses front-end technologies to create HTML, CSS, and JS that run on one of the following operating systems:

• Windows
• Windows Phone
• OSX
• iOS
• Android
• Ubuntu (or some flavor of )
• Chromium

These operating systems typically run on one or more of the following devices:

• Desktop computer
• Laptop / Netbook computer
• Mobile phone
• Tablet
• TV
• Watch
• Things (i.e. anything you can imagine, car, refrigerator, lights, thermostat etc..)

image source: https://ams-ix.net/newsitems/87

Generally speaking, front-end technologies can run on the aforementioned operating systems and devices using the following run time scenarios:

• A web browser (e.g. Chrome, IE, Safari, Firefox) running from OS
• A headless browser (e.g. phantomJS) driven from a CLI running on OS
• A WebView/browser embedded within a native application as a runtime with bridged to native API's. UI is all web based. (e.g. Apache Cordova, NW.js, Electron)
• A native application built from web tech that is interpreted at runtime with a bridge to native API's. UI is native based. (e.g. NativeScript, React Native)