Total return is the whole gain or loss an investment produced over a period, counting both the change in its value and the income it distributed, with the income assumed to have been reinvested. Its opposite number is the price return, which counts the value change only. The gap between the two is everything the investment paid out while you held it, and for an income-heavy holding that gap is most of the answer.
The phrase most often seen in fund documents is not "total return" on its own but "average annual total return," and the difference is the one worth clearing up. Total return is the plain measure of what an investment produced over the actual period. The average annual version converts that result into an equivalent per-year rate so periods of different lengths can be compared, which is the operation the annualized return covers. This page is about what goes into the number before anyone annualizes it.