Learning DNS

DNS Resource Records

A records map a hostname to an IPv4 address
AAAA records map a hostname to an IPv6 address
CNAME records, also known as aliases, map a hostname to another hostname
MX records resolve mail records pointing to an email server
TXT records are records which store textual information
NS records are nameserver records for the domain
SOA records are the start of authority records for the domain
SRV records specify particular information about a service
PTR records are pointer records resolving an IP address to a hostname

Types of DNS Servers

Primary Nameservers, previously known as Master Namservers, are the source of truth for a zone.
Secondary Nameservers, previously known as Slave Nameservers, perform zone transfers from the primary nameserver and served the zone data authoritatively.
Recursive Nameservers are nameservers that perform the recursion for a DNS query, performing DNS queries at the necessary authoritative nameservers and subsequently replying to client queries with the information gathered.
Caching Nameservers, typically also recursive nameservers, cache the DNS responses they receive, respecting the TTL values, and thus speeding up DNS resolution for clients.
Authoritative Nameservers are the primary and secondary nameservers for a zone.