F.I.R.E. is an acronym for Financial Independence Retire Early.
The main principles are to save aggressively (50-70% of income), live frugally, and invest responsibly, predominantly with low-cost index funds.
The ultimate goal is to earn enough from investments to cover expenses (i.e. Financial Independence), giving people the ability to retire. With this independence comes the freedom to spend time on interests, hobbies, side hustles, family,....without the obligation of spending time at work. To many, the most important commodity isn't money, but time.