Return, growth rate and whether a deal is worth doing. These work from actual cash flows rather than a single headline percentage, because the headline number usually hides the timing.
The distinction that matters most here is between total return and annualised return. A 40% gain sounds impressive until you learn it took eight years. CAGR and the annualised figure in the ROI calculator exist to make returns over different periods genuinely comparable.
NPV and IRR go further by accounting for when money moves, not just how much. A dollar returned next year is worth more than a dollar returned in year ten, and for anything with irregular cash flows - a rental property, a business project - that timing is often the whole story. Payback period answers the simpler question of when you get your money back, and the discounted version accounts for that same timing effect.