What is the difference between static and dynamic (shared) libraries?

A static library (.a/.lib) is copied into the executable at link time—larger binary, no runtime dependency, updates require relinking. A dynamic/shared library (.so/.dll) is linked at load/run time—smaller executables, shared across programs, updatable without relinking, but the library must be present at runtime and version compatibility matters. The choice trades deployment simplicity against flexibility and size.

g++ main.o -lmylib          # link against libmylib (static or shared)