What does FIRE actually stand for and what is the core idea behind it?

FIRE stands for Financial Independence, Retire Early. The core idea is to save and invest an unusually large share of your income so that your portfolio can eventually cover your living expenses indefinitely, freeing you from needing a paycheck. "Financial independence" means your investments generate enough to fund your lifestyle; "retire early" is the optional part, since many people who reach FI keep working on their own terms.

The movement grew out of simple math popularized by writers like Mr. Money Mustache and the classic book Your Money or Your Life: spend far less than you earn, invest the difference in low-cost index funds, and let compounding do the rest. WealthSerene's FIRE Calculator at wealthserene.com/tools/fire-calculator estimates your personal timeline based on your savings rate and target expenses.