Is my cactus sick?

[Mayday]

Hello!

I was offered a cactus many years ago and I've been trying to make it survive. Let's just say I really don't have a green thumb ( who knew cacti needed maintenance! ). This cactus is mainly an indoor cactus ( a take in out max 2 months a year because I live in Quebec, Canada ). I've noticed for many months now that it looks like there is a dried up outer layer mainly at the bottom of the cactus. However, there are new "buds" still growing. Should I do anything? Also, what is this type of cactus? How often should I water it? For now, I just feel the soil and if I think it's really dry, I water it.

Thanks for you help!

[purpleinopp]

It looks like it may have spider mites. There is webbing all over it.