I'm interested in making some modifications to the default theme. I understand how to do it, but before I start editing css and php files, I wanted to know:
-is it usual to simply copy the default (or other) theme, activate the new one and edit away?
-or is there a way to do a "sub-theme" where the original theme files are unmodified and easily upgraded, while making separate files for modification? This is the way it's done in drupal, just wondered if wordpress was the same and didn't see anything in the documentation either way.