CLR Host in .Net Framework describes interfaces that unmanaged hosts can use to integrate the common language runtime (CLR) in the .NET Framework 4, .NET Framework 4.5, and later versions into their applications. These interfaces provide methods for a host to configure and load the runtime into a process.
A CLR host is an application that is responsible for loading the CLR into a process, creating application domains within the process, and executing user code within the application domains.
Examples of CLR hosts are as follows:
ASP.Net, Internet Explorer, Shell Executables, Database Engines, Personal Organizers