in php i came accross the function checkdnsrr. optionally, you can enter one of the following dns record types:
A, MX, NS, SOA, PTR, CNAME, AAAA, or ANY. The default is MX.

i have no idea what any of them mean but wanted to use this function to verify e-mail address domains and links in real-time.

thanks. that somewhat helps.
sorting through the data and after some googling i found the following:

A = address (i think it means you give it a domain name and it will check for an ip address)
MX = mail exchange (i'll use it to verify e-mail addresses)
NS = name server
SOA = start of authority (the first record in every properly configured zone, contains info about the zone)
PTR = pointer (looks to be same as CNAME except instead of you would enter
CNAME = canonical name (the real name of a host - i think this means if you give it an ip address, it'll check to see if there's a domain name associated with it)
AAAA = IPv6 address (IPv6 increases IP address size from 32 to 128 bits for more levels of hierarchy)
ANY = i take it that means all of the above.

sites i found helpful:

please correct me if i interpreted the info wrong. hope this helps people.

I highly recommend picking up a book or ebook on DNS.