Modelsim: compiling into libraries

Hi all,

I've a few questions regarding Modelsim:

1) libraries contain the VHDL files or the result of the compilation of these files?

2) How can I compile a file in a directory by my choice, different from the work directory?

3) In a testbench, i saw this:

library work;

use work.lib_one.all;

use work.lib_two.all;

This means that in work directory there are subdirectories named lib_one, lib_two, and in those subdirectories there were compiled some VHDL files.

How can I create subdirectories of WORK and compile there VHDL files?

Thanks a lot for your answers.