A precompiled header is a header file that has statically compiled but still separate from its final executable in order to speed up compilation of dependent files.
In C and C++, precompiled headers allow for quicker compilation times by keeping the definitions from a given header in an compiled state. This allows the compiler to quickly incorporate the header when a file dependent on the header is being compiled.
Rather than having to parse through code, precompiled headers allow the compiler to skip directly to a more intermediate state. For headers that are used frequently this can result in significant compile-time savings.
