what is the purpose of Id in drupal .info

Question

In Drupal , what is ;$Id$?

I know we use this in the .info file, which tells Drupal our module information.

My question is why is ;$Id$ necessary?

Answer 1

$Id$ is the concurrent versions system (CVS) identification tag. If we want to share our module with others by checking it into Drupal’s contributed modules repository, this value will automatically be replaced by CVS.