Why did my site crash when I moved module and theme folders? A little background, I am quite new to Drupal and IT in general, so this may be a silly/basic question (I am going to start learning HTML, CSS, PHP, etc. for Drupal). I first set up my Drupal site by following the steps on drupalize.me, and then I installed the Sublime Text Editor 3. I realized I had already installed some contributed modules and the Bootstrap theme from drupal.org, but I didn't have contrib and custom folders for modules and themes, both. So I created them and moved the contributed module folders to the contrib folder under 'modules'. I also moved the contributed Bootstrap theme folder to the newly created contrib folder under themes. Then I tried to load my website but it said 'The website has encountered an unexpected error'.

What went wrong here and how can I move my already installed modules and themes correctly to their respective contrib folders?
Drupal keeps an extensive cache of all functions in (contrib) modules and the files in which those functions can be found. Since you moved the files, Drupal is probably attempting to call a function from a file that is no longer there. (It should have thrown a more detailed error in your webserver log.)

Steps to repair could be to move the files back to their original position (Drupal works fine without contrib and custom folders, but it might be easier for yourself). Or enter the database and attempt to empty all tables that end in _cache. That should make Drupal reïndex the functions.