What compiler is in Visual Studio 2015

They have their own compiler that goes by Visual C++ _____

Here is a mapping of the IDE version to the compiler version. They generally release a major compiler version with each major IDE version.

So to explicitly answer your question, Visual Studio 2015 uses the compiler Visual C++ 14.0

You can get some useful information running this:

#include <stdio.h>

int main()
{
    printf("_MSC_VER : %d \n", _MSC_VER);
    printf("_MSC_FULL_VER : %d \n", _MSC_FULL_VER);
    printf("_MSC_BUILD : %d \n", _MSC_BUILD);

    #ifdef _MSVC_LANG
        printf("_MSVC_LANG : C++%d \n", (_MSVC_LANG/100)%2000);
    #endif

    return 0;
}

Common MSVC versions:

MSVC++ 9.0 _MSC_VER == 1500 (Visual Studio 2008)

MSVC++ 10.0 _MSC_VER == 1600 (Visual Studio 2010)

MSVC++ 11.0 _MSC_VER == 1700 (Visual Studio 2012)

MSVC++ 12.0 _MSC_VER == 1800 (Visual Studio 2013)

MSVC++ 14.0 _MSC_VER == 1900 (Visual Studio 2015)

MSVC++ 14.1 _MSC_VER == 1910 (Visual Studio 2017)

Macros interpretation:

_MSVC_LANG : Defined as an integer literal that specifies the C++ language standard targeted by the compiler

_MSC_VER : contains the major and minor version numbers as an integer (e.g. "1500" is version 15.00)

_MSC_FULL_VER : contains the major version, minor version, and build numbers as an integer (e.g. "150020706" is version 15.00.20706)

_MSC_BUILD : contains the revision number after the major version, minor version, and build numbers (e.g. "1" is revision 1, such as for 15.00.20706.01)