title: If NetStandard target platform is just an interface, where/when do you write the implementation?
body: <p>I am very confused with the technical aspect of the NetStandard target platform.</p>
  <p>My only understanding is that its just an interface. This concept make sense.
  But now here is where my first confusion is:</p>
  <p>How can it be just an interface if the developer writes actual code in the said project?</p>
  <p>Second confusion:</p>
  <p>How and when does the actual implementation/DLL for a NetStandard DLL get resolved and thus used?</p>