This chapter provides the traditional speech act theory proposed by John L. Austin and later developed by John R. Searle as background knowledge, including types of speech acts and different illocutionary acts that can be performed by the speakers in saying something. Classifications of speech acts on the basis of different approaches proposed by the founder of this theory are then presented. Crucial factors for interpreting speech acts, including linguistic as well as contextual conditions, are examined as the contribution to the understanding of the intended meaning of speech acts in communication.