Thanks Steve for a very helpful explanation and set of links.
Sorry, am now hoping for a bit more spoon-feeding. You said:-
“Google has also created a data highlighter tool which you can access in WMT, where you can point and click at content and tell Google that way.”
What's WMT please? Can I find it even though I don't use Chrome?
Have thought that if I go to my Google account the data highlighter tool will probably be there?
Will start investigating typical search terms for my site and see what the new approach "does" to them.
I worry there may be no particular benefit in the new system for a site like mine which is designed to appeal to the smallish minority of searchers thinly scattered in most English regions who're willing to pay for good careers counselling.
I still appear to be on page 1 of Google for most of the terms I'd expect to be but the new system seems a lot less useful than the old as a handy guide to my competitors.
What do others think?