The "Runtime" aspect of the package refers to the fact that these libraries are used while the program is actually running (executing). Because these libraries handle memory management and system interactions, they are a target for malware.
When you see an error like
The is a collection of these standard libraries. It contains the code required to run applications developed using Visual C++ 2010. microsoft visual c++ 2010 redistributable package
If you’re looking for the (or parts) of this package, here’s what it typically includes: The "Runtime" aspect of the package refers to