Definition
CoreCLR is the virtual machine that runs .NET applications outside Unity. It loads managed assemblies, compiles IL to machine code just in time, and manages memory with a generational garbage collector. Unity has been replacing Mono with CoreCLR so the engine can use current C# language versions and the standard .NET libraries.
Relevance
CoreCLR changes which runtime executes the IL. A Unity player on CoreCLR still ships managed assemblies, and it can use current C# and the standard .NET libraries that Mono could not.
Example
A project upgrades to a Unity version that runs on CoreCLR. The player starts faster and the garbage collector pauses less. The game scripts are still managed assemblies in the Managed folder.
Connected
Synonyms
.NET runtime