How does SVN keep track of what repo it has checked out?

[richardcavell]

Hi, everyone.

I realize that my working copy has a .svn directory with information in 
it that SVN uses.  In the book, it says on page 19 (page 41 of the pdf):
"If you accidentally remove the .svn subdirectory, the easiest way to 
fix the problem is to remove the entire containing dir- ectory (a 
normal system deletion, not svn delete), then run svn update from a 
parent directory. The Subversion client will download the directory 
you've deleted, with a new .svn area as well."
Now, if you've removed the .svn directory, how does svn 'know' which 
repo you're using?  Does SVN store information somewhere else?
I had a repo checked out and I wanted to un-checkout it - that is to 
say, stop using that repo.  I was told that the simplest way would be 
to just delete the .svn directory.  Is it acceptable to do this?  Or 
have I left debris on my system by doing so?
Richard