The rule you've asked about is commonly used by the avahi daemon on Linux to listen for mDNS queries.
That iptables rule is allowing incoming udp packets on port 5353 that are destined for the multicast address 18.104.22.168. IANA defines multicast address usage here, and the mDNS RFC is here.
iptables -L -n output shown is not the complete picture, as the original match in your INPUT chain might feature more detailed packet matching based on source, the interface(s) these packets are allowed on, and a variety of other attributes. The initial match in the INPUT chain may also jump to other chains before hitting this later rule in the "IN_ZONE_work_allow" chain. To get a better understanding of all the packet attributes that must be present in order for this rule to be triggered, you must work backwards from this chain up to the first time
IN_ZONE_work_allow is seen in the
target column, then continue in that manner until you find the first jump from INPUT (assuming that this is not actually a forwarding ruleset). In your case most likely, this chain is jumped to directly from INPUT, as evidenced by the note after the chain name: "1 references". I find it much more direct to just look at the output of
iptables-save if such is available on the box.