When building software the most common scenario is that you have a team building the solution, application and/or service. You typically have front-end, back-end and full-stack developers, you have testers and designers, and more. However, working in a team is not always easy. Back in the days we could all have our software running locally and we just grabbed the latest version/commit and hacked away. For web applications the use of localhost worked just fine for almost everyone.