Domain Name System is a hierarchical distributed naming system for computer, printer, service, website, etc it corespond to 1 IP Address. It was invented so that people can remember only the computer name or website name. Imagine wihtout DNS, people needs to memorize all ip address each computer, printer or website.
read more on ---> http://en.wikipedia.org/wiki/Domain_Name_System
Wi-Fi is a local area wireless technolgy, which allow devices to send/receive data wirelessly, by 2020 80% of all devices in the world is connected using wireless.
read more on ---> http://en.wikipedia.org/wiki/Wi-Fi
What is Proxy Server?
Proxy Server is a server that receives http request first then route the request to the corresponding server or resources. It simplify and control all http traffic.
read more on ---> http://en.wikipedia.org/wiki/Proxy_server