What is F.I.R.E and how did Raj Shamani retire at age 24?

In a recent podcast with TOI and StockGro, Raj Shamani explained that F.I.R.E stands for Financial Independence, Retire Early (FIRE), which means people are trying to gain financial independence by making enough wealth and cutting their expenses so that they can retire extremely early. He mentioned that he became financially free at age 24.