MEMS means Micro-Electro-Mechanical Systems, iow. a category of a type of sensor/actor elements that work with mechanical effects but are minuscule and often constructed using lithographic processes, not milled or the like.

Memristors are a specific electric component.

https://en.wikipedia.org/wiki/Microelectromechanical_systems

https://en.wikipedia.org/wiki/Memristor

While MEMS is already huge and still getting way bigger, memristors ain't really a thing yet.

Comments felt like they conflated them. Also what are all the MEMS chips in phones? Another element of the threads is they're all over phone builds. The accelerometer? The lens systems?

Most often microphones, but yes also IMUs which provide, among other things, the acceleration data. Lens system less so, at least to my knowledge.