I had no idea how to create child themes. WordPress gave instructions but everytime I tried to follow them, I would just end up creating a disaster. With this little plugin, I've made a child of my theme in seconds. So now my cycling tour and bike hire website is up and running.
Obviously, I had to go back to the WordPress codex and work out how to include my customizations. But the hard work was taken out by this little plugin by giving me the child I've always wanted!
PS ... if you need to know how to add customizations to the php pages you amended, and you can't understand the codex (because it's written by a nerd who knows PHP and assumes we all do), it's simple:
Except for the functions.php file, just copy the PHP files that you amended in your parent theme's folder into your child theme folder using FTP.
As regards any changes you made to your functions.php file, I've no idea what to do there - I don't know much about PHP - but I do know that if you follow the instructions in the codex word-for-word, you'll end up taking down your site.