input-method is the translation of one or more keystrokes into a language character. Most languages have their own input method; some input methods are shared by several languages, and some languages have more than one input method.
The simplest kind of input method is a straight mapping of a key into a symbol in another language. For example, in the russian-typewriter input method, pressing the key
a produces the letter
ф. Other languages use compostion: two or more keystrokes are converted to a single letter. For example, with the french-prefix input method, typing
'e produces the symbol
More complex input-methods are used for languages like Mandarin and Japanese. This is described in the manual node (emacs) Input Methods. Useful commands include:
C-\:: Enable or disable use of the selected input method (
C-x <RET> C-\ METHOD <RET>:: Select a new input method for the current buffer (
C-h I METHOD <RET>or
C-h C-\ METHOD <RET>:: Describe the input method METHOD (
describe-input-method). By default, it describes the current input method (if any). This description should give you the full details of how to use any particular input method.
M-x list-input-methods:: Display a list of all the supported input methods.