Thread: What is a Runtime Library in C/C++

hi all,
After read about Runtime Library at:
Difference between C/C++ Runtime Library and C/C++ Standard Library. - Stack Overflow

finally, I have not still understand : What is a Runtime Library ?, why printf, fopen,... is a part of Runtime Library ?
Please explain more detail about C/C++ Runtime Library , add examples is great.

Runtime library is different to Dynamic library ?

Thanks ,
thavali