svchost.exe is (like the name says) the host for all services, which are spread over the several svchost.exe processes. You can view the list of (running) services by clicking Start -> Run -> services.msc -> OK.
With Sysinternals Process Explorer you can also take a look which services run under which svchost.exe (see screenshot) You can download Process Explorer from http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx
It is possible to stop services for example Tablet PC Input Device if you don’t use that kind of input, but be carefull! You can look what services are safe to shut down by looking for example on the website http://www.blackviper.com/WinVista/servicecfg.htm