HD is the term used to differentiate the systems that generate, transmit or support HD content (High Definition) with those of standard definition or low definition (SD).

HD resolutions are usually at least 1280 x 720 pixels by taking the ratio "width x height". Being the height, 720 pixels, which make high resolution.

Voice over IP, also called Voice over IP, VoIP, VoIP (VoIP by its acronym in English, Voice over IP) is a group of resources that enable the voice signal to travel over the Internet using a IP (Internet Protocol). This means that the voice signal in digital form is sent, in data packets, instead of sending it in analog form through circuits used for telephony onlyconventional and PSTN networks (acronym for Public Switched Telephone Network, Public Switched Telephone Network).

The Wifi technology is a wireless communication mechanism between devices. This technology allows you to connect devices such as computers, laptops, mobile etc... to the Internet or communicate with the devices themselves.

Applications can be several, among the most common are the access points, ideal for giving and sharing a connection signal to multiple devices. It is the typical configuration of a home user.
Repeater, ideal to repeat and amplify weak signal.

The power and range between devices basically depends on the antenna and its hardware.

The wireless signals work under a unified standard regulations, the standard that is based on the IEEE 802.11. These include IEEE 802.11b, IEEE 802.11g and IEEE 802.11n working at 11 Mbit/s, 54 Mbit/s and 300 Mbit/s, respectively.
Being any device with a standardized protocol such technology can connect to another using the same technology, making it a kind of universal connection.

The wireless networks are characterized by the ease and convenience of making connections in infrastructure, since it is not necessary to perform network cable installations.
it also allows connecting a lot of devices to a single node.