macOS has had IPv6 support for some time.
Whether or not your ISP provides support, every IPv6-capable device assigns itself a “link local” address (which all begin with
fe80::. These addresses are automatically created by each device without any configuration or servers. Link local addresses are not routable and can therefore only be used on a single LAN segment, but they allow devices that are connected locally to communicate with each other without needing any configuration other than enabling IPv6 itself.
If your ISP supports IPv6, then you may have other (globally routable) IPv6 addresses in addition to the link-local addresses. These may come from an IPv6 DHCP server (maybe part of your router) or they may be auto-generated from the address block assigned by your ISP using IPv6’s Stateless Address Autoconfiguration protocol.
In terms of how to understand them, Wireshark should do all the ugly work decoding the packets. The IPv6 headers are different, but the layer-4 protocol (TCP, UDP, etc.) carried by it is the same.