How does Housecall work?

Could you please elaborate on the functioning of Housecall? I'm particularly interested in understanding how it operates and what makes it unique compared to other similar services. I'm curious about its CORE features, the process involved in availing its services, and any specific benefits or advantages it offers to users. Additionally, I'd like to know if there are any limitations or requirements that users need to be aware of before utilizing Housecall.