Depending on where you go, these two terms may actually be used interchangeably. Alzheimer’s Special Care Units (SCUs) may refer to wings of a senior living community where those with more advanced Alzheimer’s receive their care — at the same time, this may also include more mild cases of dementia as well.
It really depends on the specifics of your community, although it’s good to know these two terms exist in order to ask the right questions during a tour or interview!