`vcomp120.dll` is a dynamic link library (DLL) file provided by Microsoft and is associated with Microsoft® Visual Studio®. This DLL is specifically related to the Microsoft® C/C++ OpenMP Runtime. OpenMP (Open Multi-Processing) is an API that supports multi-platform shared memory multiprocessing programming in C, C++, and Fortran on many architectures, including Unix-like systems and Microsoft Windows platforms. The "120" in `vcomp120.dll` indicates that this DLL is from the Visual Studio 2013 version. Each version of Visual Studio will have a different number corresponding to its release. This file is used to parallelize code sections with ease using OpenMP, allowing the code to run on multiple cores simultaneously, enhancing performance.

If users or developers face issues with `vcomp120.dll`, it might be due to the file being missing, outdated, or corrupted. Such problems can arise if software that relies on this DLL is being run on a system where Visual Studio 2013 redistributables aren't installed or if there's some issue with the installation. The usual solution is to either install or repair the Microsoft Visual C++ 2013 Redistributable package. If the issue is specific to an application, ensuring the application itself is updated can also help.