title: What exactly is a "library" in a crate?
body: <p>I'm a little confused about the concept &quot;library&quot; in rust, which is mentioned from &quot;A crate is a binary or library&quot;.</p>
  <p>If I'm right, a binary means an executable program (which can be run from shell, for example), but what is a library?</p>
  <p>Are they some sort of object files with symbols like .a or .so, which will be linked to my program (like C/C++)</p>
  <p>Or they are pure source codes which will be compiled together with my program?</p>