Speech act theory is attributed to

Speech act theory is attributed to the Oxford philosopher J. L. Austin. The basic ideas, which were formed by him in the late 1930s, were presented in his lectures given at Oxford in 1952–1954, and later in his William James Lectures delivered at Harvard in 1955. These lectures were finally published posthumously as How To Do Things With Words in 1962. In that book, Austin ( 1962: 94) told that to say something is to do something, or in saying something, and even by saying something we do something.
Speech acts explain when people want to express themselves, they do not only produce utterances containing grammatical structures and words, they perform actions via those utterances. If you work in a situation where a boss has a great deal of power, then the boss’s utterance of the expression is more than just statement.
(1)You’re fired.
The utterance in (1) can be used to perform the act of ending your employment. However, the actions performed by utterances do not have to be as dramatic or as unpleasant as in (1). The action can be quit pleasant, as in the compliment performed by (2.a), the acknowledgement of thanks in [2.b], or the expression of surprise in [2.c].
(2.a) You’re delicious.
(2.b) You’re welcome.
(2.c) You’re crazy.
Generally, Speech acts are actions performed via utterances, in English, are commonly given more specific labels, such as apology, complaint, compliment, invitation, promise, or request.
Austin claimed that all utterances, in addition to meaning whatever they mean, perform specific acts via the specific communicative force of an utterance. Furthermore, he introduced a threefold distinction among the acts one simultaneously performs when saying something, as illustrated in:
(i) Locutionary act: the production of a meaningful linguistic expression.
(ii) Illocutionary act: the action intended to be performed by a speaker in uttering a linguistic expression, by virtue of the conventional force associated with it, either explicitly or implicitly.
(iii) Perlocutionary act: the bringing about of consequences or effects on the audience through the uttering of a linguistic expression, such consequences or effects being special to the circumstances of utterance.