Using KDE/Shortcuts

Default Shortcut Table
Updated for Plasma 5 (KDE5)

Alt-Tab or Alt-Shift-Tab

Cycle through open applications

Ctrl-Tab or Ctrl-Shift-Tab

Cycle through application specific tabs or panes. Previously (KDE4) Cycle through your desktops.

Alt-F1

Open KDE Application Launcher (although not krunner, see Alt+F2). Start typing to narrow down results. Similar to Microsoft Windows Start Menu.

Alt+F2

Application launcher, command line and more (krunner in Plasma 5). Allows quick launching applications by typing their name (kmail, k3b, ...)

Alt-F3

Window Menu for specific application. Useful for Send to. . . Desktop/Screen or Minimize/Maximize with just the keyboard. Similar to Alt+Space in Microsoft Windows

Alt-F4

Close the current window

Ctrl-F{1..8}

Switch to a specific desktop

Ctrl-Alt-L

Lock your session. This will display a box with a password area for you to login back into your session, and a button that will allow someone else to login while keeping your session active.

Ctrl-Alt-Del

Display logout screen. You have 4 choices : Suspend, close your session, turn off your computer and restart your computer.

Ctrl-Esc

System Activity (similar to Microsoft Windows Task Manager). Show running processes, CPU, MEM, etc.

Ctrl-Alt-Esc

Window destroyer (every window you click on will be destroyed). Press Esc to cancel the killer cursor.

The following are shortcut keys that control X11:
Ctrl-Alt-Backspace

This exits KDE (without saving!) Use this as a last resort.

Ctrl-Alt-Numpad +

Zoom in using the next screen resolution. You may need to configure this in your X-Server configuration for it to work

Ctrl-Alt-Numpad -

Zoom out using the previous screen resolution. You may need to configure this in your X-Server configuration for it to work.

Win-Q Displays the Activities list

Win-Tab Switches to next Activity

Defining own shortcuts
You may not be happy with the predefined shortcuts but you can easily redefine existing shortcuts, or define your own. All you need to do is open KMenu -> Control Center-> Regional & Accessibility -> Keyboard Shortcuts. The interface of this is self-explanatory.

Here is the list of thing you may do with defined shortcuts:
 * 1) opening apps very quickly,
 * 2) kill, start, restart daemons,
 * 3) send commands to running apps...