EBITDA stands for earnings before interest, tax, depreciation, and amortization. Start from operating income, which already excludes interest and tax. Then add D&A back on, since it is a paper charge for past purchases, not cash leaving this year. What remains is a rough measure of the cash the operations generate, stripped of financing choices, tax location, and old accounting for assets, which makes companies with very different debt loads comparable.
That is its legitimate job, and it is the bottom half of EV/EBITDA. Its abuse is being treated as free cash flow: EBITDA ignores the real cash needed to maintain equipment and the real interest actually paid. Charlie Munger called it "bullshit earnings," a warning worth remembering whenever a struggling company leads with EBITDA.