Can gcc and Linux create a dynamic library?

[ali hagigat]

My question is about dynamic libraries and shared libraries in Linux
and their differences.

Is it possible to create a dynamic library by gcc?

Is my following understanding from a dynamic library OK?

I think a dynamic library is added to the address space of a running
code in run time.
If program A uses a dynamic library and in run time A references a
variable(not inside the code of A), then the code of that library is
added to the address space of A.

If another program B has been linked with the same library dynamically
and B references a variable (not inside the code of B), then the code
of that library is added to the address space of B too.

This concept is different with a shared library which its code is put
into the memory only once and many programs use it.  Is that right?