Those hosts are DNSseeds.
When your node starts if it find itself unable to successfully connect to the network within 11 seconds it will query those DNS names which are run by technical people in the Bitcoin community, and get back a lists of recently working nodes.
The use of DNS improves your privacy somewhat since DNS caching can prevent the operator's name server from seeing the request at all and if it isn't cached they usually won't see your IP address, instead they'll see the IP of your ISPs recursive resolver. (Of course, the fact that it skips the use of it entirely if it can get connected also improves your privacy).
You can disable use of these dnsseeds by setting -dnsseed=0.