A mobile-first approach to styling means that styles are applied first to mobile devices. Advanced styles and other overrides for larger screens are then added into the stylesheet via media queries…
Getting back to basics, before a website or app is released, most of them go through three preliminary stages. These stages allow the team, and sometimes a few select users, to test its appearance, structure, and functionality before its release. Ideally, these preliminary stages allow you to fix any problems while they’re still small, and fine-tune your design to communicate your message most clearly.
But because these phases are similar, they’re often confused with each other. That’s why we’ll take a moment here to clarify the proper terminology for each. Marcin Treder lists the three formative stages of the UX design process as wireframes, mockups, and prototypes. Let’s take a deeper look at each stage.