All of the above really, but as FishyFolk said, I would still emphasise the learning of:
where ,when and what to forage in yout different environments .
Not just learning about the edibles but also plants for other purposes, like medicine , cordage and/or building materials and so on...
That is probably my favourite subject of all...
Richard Mabey has written some really great books on the subject ...
"Plants with purpose" and "Food for free" (Collins gem) , to mention just a few, relevant to the UK.
Hope it helps...