Cumulative return is the total change over a whole period, such as +50% over five years. CAGR — compound annual growth rate — is the steady yearly rate that would have produced the same result: about 8.4% a year for that +50%. It's an annualised return, and it's the smaller, more honest number, because it lets you compare periods of different lengths instead of setting a long run's big-looking total against a single year's figure.
The app's Annualised Growth figure is a CAGR with two quirks worth knowing. It measures capital growth only, leaving dividends out. And it treats all the money you've put in as if it went in on your first purchase date, so if you've added money over the years it pulls the figure towards zero: gains and losses both look smaller than they were. Treat it as a rough guide rather than a precise rate.
The same result said two ways. The yearly rate is the one you can compare.
Educational content only. It is not personal financial advice.