Wikipedia is a good place to look those up, but here is a very quick description of each:
DNS: (Domain Name System) This is one of the systems that the internet is built on. DNS helps to translate a hostname (www.espn.com) into an IP address, so that humans don't have to keep track of them...and so that your computer knows where to go when you type it.
NNTP: (Network News Transfer Protocol) Just like it sounds, it helps to transfer data between news servers (enabling Usenet, for example)
Proxy: a proxy is an application intermediary. (just like for investor groups...a "proxy vote" is made for you by someone else) Proxies are used for all sorts of things: firewalling/gateway security, web/content filtering, application redirection, etc. There are forward, transparent, and reverse proxies. SQUID, Microsoft ISA, and Blue Coat are the some of the more popular ones.
IMAP: Internet Message Access Protocol. This is one of many protocols that assists in the local retrieval of email from a remote email server. IMAP and POP are common retrieval protocols, and SMTP is the most common protocol for sending mail.