VOIP is an acronym for Voice Over IP, or in more common terms phone service over the Internet.
If you have a reasonable quality Internet connection you can get your phone service delivered to you through your Internet connection instead of from your local phone company.
Some people use VOIP in addition to their traditional phone service, since VOIP service providers usually offers lower rates than the traditional phone companies, but sometimes don't offer full 911 service, phone directory listings, 411 service, etc.
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3G: The term used to refer to the next generation of wireless communications technology, the "first generation" having been analog cellular, and the "second generation" being today's digital cellular networks. An initiative of the International Telecommunications Union (ITU) and regional standards bodies, 3G aims to provide universal, high-speed, high-bandwidth (up to 4 Mbps) wireless services supporting a variety of advanced applications.
Hint: If you want to know the definition of something, go to google, and type in "Define:", without the quotes. So for VOIP, you type:
define:voip