The point of the Microsoft.Net.Compilers package is that the compilers distributed with that package will be used for compiling your project, rather than the compiler that comes with .NET Framework or with Visual Studio. The most practical direct benefit is that it allows your projects to use C# 6 features, and then allows those projects to be built on a system that doesn't have a C# 6 compiler installed, for instance on a continuous integration server where you don't want to install the full Visual Studio 2015.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…