When looking to build a fast prototype or an MVP one of the options is to use a pre-assembled library of visual styles to speed up time to market. This is not recommended for every case, but sometimes it makes sense.
Bootstrap CSS lets us use general graphic styles so we don't have to design from scratch all the interactions and forms of our platform.
Some nerds want to know what's under the hood. We are the same kind.
Our AX3 Framework is a group of methodologies and tools, improved over the past 14 years with hundreds of projects. Here are some we use: