I am a bear of very little brain.
I used to (vaguely) understand IPv4.
I think I need to do a bit of reading up about this mystical IPv6 thingy. Just done an ipconfig on my Win10 lappie (with BT fibre router) and it's reporting 2 IPv6 addresses, plus a dozen 'Temporary IPv6 addresses' (using the prefixes of the first two) plus a link-local IPv6 address. What the heck?