What is Microsoft Visual C ++? and is it OK to delete some of them?

Visual C is a software that underpins a lot of the software that runs on the windows operating system most especially games. It is highly inadvisable to delete any of those files unless you want to find yourself having to reinstall them the next time you try to play a PC game or many internet websites.
Bottom line is it's a "don't f*ck with it" item on windows unless you really really know what you're doing.

"Many applications require redistributable Visual C++ packages to function correctly. These packages are often installed independently of applications, allowing multiple applications to make use of the package while only having to install it once. These Visual C++ redistributable and runtime packages are mostly installed for standard libraries that many applications use."