title: GitHub: What does checkout do?
body: <p>I'm coming from a perforce background, trying to understand gitHub.</p>
  
  <p>In Perforce when I "checkout" something it lets other users know I am working on that file.  Does checkout work the same way in Git?</p>
  
  <p>It seams like you don't check out files but branches?</p>
  
  <p>Thanks</p>