From one site:

"DNS translates alphanumeric names used by humans

2-part domain name (ex. cornell.edu)
3-part subdomain name (ex. ciser.cornell.edu)
4-part host name (ex. gaea.ciser.cornell.edu)

into numeric IP addresses used by computers

3-part subnet (ex. 128.253.230)
4-part host address (ex. 128.253.230.32)
"


A