A mobile emulator is a resource for emulating or simulating a mobile device or smartphone environment. It allows developers to test URLs or other technologies on a mobile device's operating system and display interface.
Techopedia explains Mobile Emulator
Part of the utility of a mobile emulator is related to responsive design, the idea that websites, Web projects and software products need to be able to work well on mobile operating systems and interfaces. A mobile emulator typically focuses on one specific mobile platform, for example, Apple iOS or Android.
Some mobile emulators are available online. By inputting a URL and choosing a device, users can get effective simulations over the Web. Other mobile emulators are sold out of the box or otherwise used offline.
The use of a mobile emulator is something that many experts consider critical for development. In addition to full-scale emulators that use simulated operating system source code, some other means of emulation are related to blueprints and schematics for early prototypes. Some experts have even suggested using a cardboard cutout and a paper feed to emulate scrolling on a mobile device. This helps developers get a feel for the layout and schematics of mobile products early on, before they actually start coding a project. With mobile device interfaces taking up so much "market share" in various parts of the tech industry, gearing products toward mobile is a major part of development and something that is very much valued in the tech community.