The Need
Sometimes people have too much stuff and not enough storage, or they just need to move some stuff out of their house for a short period of time. That's where self-storage comes in. These facilities are usually relatively large and fenced. You can generally come and go as you like, as long as it's during business hours.
The Process
When you sign up for self-storage, you get assigned a space based on the size of your need. These can be anywhere from a small walk-in sized closet to something large enough to store an RV. You sign a lease, much like renting an apartment, and you are given the codes necessary to enter the building or facility. Usually you are told to bring your own lock; that way not even the self-storage management can get in.
Loose Pieces of Information
Self-storage facilities have to carry large insurance policies that cover everyone's stuff in case the place burns down or is robbed. The lease you sign for your space usually waives a lot of your rights to sue, but it is up to the facility to ensure the security of your stuff from both fire and theft. The management will cut your lock off if they HAVE to get in to your locker (if they believe there's something dangerous in there like a bomb or something catches fire).