The Top Level Domain (TLD) is the end of the domain name to indicate the DNS server to search first.
Authoritative Name Servers
The authoritative name server is the final DNS server mapping the domain name directly to the IP address.
Reverse lookups convert the IP address to a domain name. in the format 1.0.168.192.in-addr.arpa for 192.168.0.1 for the domain.
Caching
A name server can store IP addresses for future requests for a short time to improve requests.