windows has a lot of background processes constantly running; they are called services and they perform various tasks, such as looking after your network, running windows update, diagnostics, drivers for your hardware, power policies and a load of other stuff.
windows uses the svchost program to host (run) these services, so many different services are running, using the same program.
this is a very simplified explanation, but i hope you get the idea.
this is perfectly normal behaviour, and nothing to worry about.