How to open apps in Ubuntu 12.04 to read documents, play music and video, surf the net and reading emails?
As per @devav2:
Libreoffice is like Microsoft Office and supports most of its formats.
To listen to music, you can use Rhythmbox. Video can be played with Totem.
TO surf the web, you can use Firefox, or Chromium if you install it in the Ubuntu Software Center.
To read email on your computer, use Thunderbird or Evince. You can open any of these by clicking the top left button in the launcher(dock-like thing at the left with all the buttons) and typing the name of a program. You can install many more useful things with the Ubuntu Software Center. Many applications there are free, and can be installed as easily as clicking the Install button and giving your password.
It depends on your preferences. You can simply press the super, or Win key (usually between Alt and Ctrl), or press the icon at the top of the Unity Panel (Dash Home) to bring up the Dash. If you know the name, or part of the name, of an app, file, or folder, you can simply start typing until it appears at the top-left of the list of potential targets, then press return or click on the icon. This is probably the quickest way to run a program whose name you know.
I have found that sometimes, whatever I do, the left super key will only bring up the list of keyboard shortcuts, which is very annoying; if this happens, press the corresponding right super key instead (this is the only way to dismiss the window). I think this may be a bug, since it isn't documented to work this way
If you don't know the name of the program or document, then notice that at the bottom of the panel that appears, you'll see several icons, which represent filters, or lenses, that categorize what is shown. You can click on these, or press Ctrl + Tab to cycle through them. The second one on the left is a list of all apps, and can lead you to any app either installed or potentially installable.
If you want to open a music file, and you know the name, it's better to search for this than to open an app, then search for the music file. This is considered a more modern method of user interface; you don't need to care about the name of the application that is used to open your file. In fact, the application name can change, but your method of opening the file doesn't need to change in that case.