Yeah, SLAAC is stateless autoconfig for ipv6. It's a little like DHCP in that the client gets an address automatically but it's handled by the client machine rather than having a DHCP server running.

SLAAC capable machines give themselves an address based on the ipv6 prefix advertised on the network then do a duplicate address check with all of the other devices to make sure they're unique and away you go. There's no central tracking of all dynamic addresses on the network segment, hence the stateless part of the name, but you can poll them with a neighbor request or broadcast ping when you want to see what's there. The benefit is that basically everything you plug into your network probably supports SLAAC out of the box without needing to run server software anywhere to delegate addresses so new v6 clients just work without specific configuration.

If the client supports it you can specify a SLAAC token that the machine will combine with the advertised network prefix rather than generating its own, which is how I have pihole showing up at ::253 as well as its DHCPv4 assigned ...253. It's a convenient configuration.

I'd ignored SLAAC the first time around and given everything static v6 addresses without realizing that my provider would periodically change my prefix. That was fun to untangle, things worked if they made v4 requests but failed over v6 whenever my prefix changed so the failure mode appeared to be somewhat random depending on whether the service or application supported dual stack and was trying to connect over broken v6. Fun times.