SPEECH ACT

We use the term speech act to describe  actions such "requesting", "comanding", "questioning" or "informing". 
We can define speech act as the action performed by a speaker with a utterance. If you say "I´ll be there at six", you´re not just speaking,  you seem to be performing the speech act of "promising".
 
J.L. Austin analyses speech acts on three levels:

• Locutionary act:      Wen we say something.  1.- Phonic act: To emit a sound.

                                                                                      2.- Phatic act: To emit words.     
                                                                                      
                                                                                      3.- Retic act: Use of sounds and words with                                                                                        meaning.

• Ilocutionary act: the semantic 'illocutionary force' of the utterance, thus its real, intended meanin.
• Perlocutionary act: its actual effect, such as persuading, convincing, scaring, enlightening, inspiring, or otherwise getting someone to do or realize something, whether intended or not (Austin 1962).

 

J.L Austin.