An epoxy floor is built in layers. The concrete is prepared mechanically so the coating can bond, then a primer and one or more coats of resin are installed. Decorative material such as vinyl flake, quartz, or metallic pigment can be added between coats, and a clear topcoat protects the result.
The value of a coating system is that you're choosing the finished surface rather than inheriting whatever the slab looks like. Color, texture, slip resistance, and thickness are all decisions.
The catch is that every coating depends entirely on the preparation underneath it. A coating installed over a slick, dirty, or moisture-heavy slab will fail no matter how good the material is — which is why concrete surface preparation is not an upsell on these jobs. It's the job.