Name Description
Unbalanced Audio: In electronics, a condition where the two legs of the circuit are unbalanced with respect to ground, usually because one leg is kept at ground potential. In other words: An audio signal requires two wires or conductors to function. Unbalanced circuits tend to be less expensive to construct, but they are much more susceptible to induced noise problems than their balanced counterparts.
Undo: The Undo command is located in the Edit menu of most programs and has the shortcut "Ctrl+Z" (PC) or "Cmd-Z" (Mac). It is used to undo the most recent action performed in a program. Common events that can be undone include typing or deleting text in a word processing program, drawing or moving images in an image editor, and trimming media in a video or audio editing program. By selecting "Undo," most actions can be quickly reversed. Many programs also support "multiple undo," which makes it possible to undo several actions at once.
Unmount: Unmounting a disk makes it inaccessible by the computer. Of course, in order for a disk to be unmounted, it must first be mounted. When a disk is mounted, it is active and the computer can access its contents. Since unmounting a disk prevents the computer from accessing it, there is no risk of the disk being disconnected in the middle of a data transfer. Therefore, before removing an external data storage device, such as a USB flash drive, the disk should be unmounted to avoid possible data corruption.
Upload: While downloading is receiving a file from another computer, uploading is the exact opposite. It is sending a file from your computer to another system. Pretty straight forward. It is possible to upload and download at the same time, but it may cause slower transfer speeds, especially if you have a low bandwidth connection. Because most files are located on Internet servers, people generally do a lot more downloading than uploading.
UPnP Stands for "Universal Plug and Play." Plug and Play describes devices that work with a computer system as soon as they are connected. UPnP is an extension of this idea that expands the range of Plug and Play devices to networking equipment. Universal Plug and Play uses network protocols to allow a wide range of devices to be interconnected and work seamlessly with each other. UPnP devices can be connected via wired (i.e. Ethernet and Firewire) or wireless (i.e. Wi-Fi and Bluetooth) connections. As long as a product supports UPnP, it can communicate with other UPnP devices within a network. The connections are typically created using the DHCP networking protocol, which assigns each connected device a unique IP address.
URL: Stands for "Uniform Resource Locator." A URL is the address of a specific Web site or file on the Internet. It cannot have spaces or certain other characters and uses forward slashes to denote different directories. Some examples of URLs are http://www.cnet.com/, http://web.mit.edu/, and ftp://info.apple.com/. As you can see, not all URLs begin with "http". The first part of a URL indicates what kind of resource it is addressing. Here is a list of the different resource prefixes:

    http - a hypertext directory or document (such as a Web page)
       ftp - a directory of files or an actual file available to download
         gopher - a gopher document or menu
         telnet - anix-based computer system that you can log into
       news - a newsgroup
         WAIS - a database or document on a Wide Area Information Search database
        file - a file located on your hard drive or some other local drive
USB: Stands for "Universal Serial Bus." USB is the most common type of computer port used in today's computers. It can be used to connect keyboards, mice, game controllers, printers, scanners, digital cameras, and removable media drives, just to name a few. 
User Interface: A user interface is the means in which a user controls a software program or hardware device. For example, a software interface may include windows, icons, menus, and buttons that allow the user to interact with the program. This is also known as a graphical user interface, or GUI. A hardware interface can be a remote control or a video game controller. It may also refer to the controls on a camcorder, digital camera, or iPod. Most modern user interfaces today are designed using a combination of hardware and software.
Username: A username is a name that uniquely identifies someone on a computer system. For example, a computer may be setup with multiple accounts, with different usernames for each account. Many websites allow users to choose a username so that they can customize their settings or set up an online account. For example, your bank may allow you to choose a username for accessing your banking information. You may need to choose a username in order to post messages to a certain message board on the Web. E-mail services, such as Live.com mail require users to choose a username in order to use the service.
Utility: Utility programs, commonly referred to as just "utilities," are software programs that add functionality to your computer or help your computer perform better. These include antivirus, backup, disk repair, file management, security, and networking programs. Utilities can also be applications such as screensavers, font and icon tools, and desktop enhancements. Some utility programs help keep your computer free from unwanted software such as viruses or spyware, while others add functionality that allows you to customize your desktop and user interface.
UXGA: Resolution of a computer generated image. A UXGA projector will be able to display a 1600x1200 image from a computer running in a UXGA video mode. If the computer is not running in a UXGA mode, typically the projector will resize the image to 1600x1200.