I’m glad you asked.  I’m sorry, but I have limited information about this, and most of it isn’t useful.
assitant
Sometimes contracting is done privately, and isn’t something that’s generally known about.  For example, the military uses contractors to perform a wide range of tasks, and they usually don’t advertise this fact, since they don’t want to raise any alarm.
assistant
What does a contractor do?
user
A contractor is someone who is paid to provide services in an agreed upon amount of time and under a specific set of conditions.
assistant
What kind of services do they provide?
user
Contractors can provide a wide range of services, from building houses to cleaning hotel rooms to delivering packages to cleaning up after disasters.  All of these jobs require a certain set of skills that the contractor will provide.
assistant
I never heard of them doing some of these things.
user