Many program, as well as VDR and it's plugins, do some common and sometimes also trivial things that many other programs do as well. To prevent reinventing the wheel over and over again, those parts are collected into libraries. Those libraries are then linked to the program binary at compilation time.
There are two possibilities to include the functions of a library into a program: statically and dynamically. With statically linking a library all function are embedded into the program binary, with dynamically linking the necessary functions are called at runtime and are not embedded into the binary.