Icon, name Explaination
Move/Release Move the mouse without clicking, or cease to click.
(Left) drag This means to hold the left mouse button (unless another button, eg. right drag is specified) and move the mouse in a certain direction or a certain point, and then release.
Click, both-click A general word for pressing a mouse button, due to the clicking sound they make. This sometimes can mean either button. Both-click is click both buttons at the same time, and is awkward enough to have been abandoned by most programs in favour of middle-clicking.
(Left[-])click However, it is much safer to assume that the word click means left-click, as left is the general-use mouse button.
Right(-)click Click with the secondary mouse button. This is called the right mouse button (RMB) because 9/10 people are right-handed. Right-clicking will either perform the second-most important function, will be used for commands that need comfirmation to help avoid accidental clicks, or will open a mini-menu to select more options.
Middle(-)click If you have a three-button mouse, or a mouse with a pressable wheel, this means your middle button. This also assumes you have your middle button set to be the middle button, and not performing any special tasks.
Scroll, mouse wheel This means that there is a two-direction control, (often something that can be moved upwards and downwards, or left and right. Sometimes something that can be rotated) and that the mouse wheel provides input.
Fourth button, thumbclick, frontclick Some programs support four/five-button mice like the newest Intellimouse. Frontclick is probably the sensible name for this, although identifying this as meaning MB4 (mouse button four) is important.
Fifth button, backclick For programs that support a fifth button. These are usually placed at the left (or right, for left-handed mice) side of the mouse, with the 4th button at the front and the fifth at the back. Hence why the name backclick is sometimes used- which seems the logical term to run with. This should not be assigned to anything that requires speed as the thumb has to slide back to this button from its default position on MB4.
Shift click
Alt click
Control click
Holding down the appropriate button and then clicking. Allows the precision of mouse control while still using the "function-swapping" properties of the keyboard.
Arrows, Arrow keys. The four directional arrow keys, situated between the number pad and the main enter key, are used as directional controls, often to move a cursor along a square or isometric grid.
W, S, A, D. On a qwerty keyboard, these are often used as a secondary arrowpad.
Left/other arrow keys An individual arrow key.
Clockwise Any key that is assigned to perform a clockwise rotation.
Anticlockwise Any key that is assigned to perform an anticlockwise rotation.
Down
Up
A key used for downwards when the directional arrows are not so assigned. Likewise for a key "unnaturally" assigned to upwards.
Enter The enter key, usually shaped like in the graphic. There is also a secondary enter key on the number pad.
Spacebar The big bar below the letter keys. Space is the short term.
Control (Ctrl) Either "control" key. These are often used for hotkeys.
Alt The alt key, usually the left one, but if your keys both read "alt" then either will likely work. This allows acess to the top menu in windows.
Alt Gr (Alternative Graphics) This always means the right alt key. It's named Alt Gr on many Continental European keyboards, as they need a second shift-like key to accomodate the extra symbols on their keyboards. On the (US) international layout it shifts the letter keys to alternative symbols, and many non-english keyboards need to use it as a second shift-key to accomodate all the symbols they need.
Shift Shift allows temporary capitals. It's used to assist keyboard shortcuts, or to shift the state the mouse is in. (shift-click)
Caps, Capslock Often used to toggle between modes. In most programs, this means letting you do allcaps (all capitals) for a short time.
Tab Allows you to quickly switch between tabbed menus, or even areas of the current window, without using the mouse. This often has special properties, and in word processors it gives you a sort of "absolute space," allowing you to line words up without using tables, and when you have a non-unispaced font. Tab is used by people who can't use mice to browse the internet.
Backspace Normally this allows you to delete a character without moving left first. This often has special functions, sometimes to do with rotation, in programs that don't involve word processing. (eg. going back in browsers)
Alt-tab Windows applications should never use both of these keys in combination, and having one of them as a "hold to perform a function" key, and the other as a "press to perform a function" key risks people switching out of that application by accident.
Numpad, Number pad. Used intensively for data managedment, and for typing characters using the altnum method. The numpad features a forwardslash, (division) a star, (multiplication) a plus, and a minus sign, (all the computer's basic mathematical signs) a second enter key, and a numlock key, to switch the mode of the remaining ten keys with numbers on them. The corner keys and the two bottom keys can also perform the functions of the six number keys (ins del home end pgup pgdn) Some programs also use it to double as an eight-directional, (or ten-directional, using zero and five for up and down) control pad.