This message is sent out to find information about other IPv6 devices on the link (the local part of the network). It might be to verify if a device is still reachable, or it could be Duplicate Address Detection (DAD), to see if there is an IP conflict.
The NS message is sent to the solicited-node multicast group. It should reach very few devices since it’s more efficient than broadcasting like ARP.
The device with the IP address in question, if it is alive and working, will respond with a Neighbour Advertisement message. This is how MAC to IP bindings can be found.