While its still not known exactly how and why rapamycin so consistently increases healthspan and lifespan, a key mechanism is thought to be through the autophagy it promotes.
The definition of autophagy is here (source):
A process by which a cell breaks down and destroys old, damaged, or abnormal proteins and other substances in its cytoplasm (the fluid inside a cell). The breakdown products are then recycled for important cell functions, especially during periods of stress or starvation. Autophagy also helps destroy bacteria and viruses that cause infection and may prevent normal cells from becoming cancer cells.
I wanted to learn more about autophagy, and specifically the different types of autophagy that have been identified, and the differences between them.
I found this 2014 paper, which seems to be a good overview: