Q.What Is The White Stuff Growing At The Base Of My Plant? If It Is Harmful, How Do I Get Rid Of It?
I have a succulent that hasn’t been doing well lately and it’s got white fuzzy stuff growing at the base.

Certified GKH Gardening Expert
The picture is not very clear. It is quite difficult to see what is going on, here, but it looks like soft scale, or mealy bugs! This is a HUGE problem, and will cause infection to your plant, and eventually, death of the plant.
These articles will help:
https://www.gardeningknowhow.com/plant-problems/pests/insects/what-is-soft-scale.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/mealybugs-control.htm