Compound Annual Growth Rate from start to end value.
Total return tells you how much you made overall; CAGR normalizes that to a per-year figure, making strategies of different durations comparable. A 50% gain over 5 years is only an 8.4% CAGR — far less impressive than it sounds.
The S&P 500 has historically returned ~10% CAGR before inflation. A trading strategy should significantly beat this threshold to justify the time and risk over passive investing.