your question is great and there are many web on that. one of that,
en.wikipedia.org/wiki/speech_acts
I think, speech act is a scientific analyzing method of language and philosophy of language. is that correct?
I think I've learned what is meant by speech acts
speech acts are acts that are performed via utterances
for instance, the utterance I'm sorry
is performing the act of apologizing
i hope that you got it
and this site you recommended is really great en.wikipedia.org/wiki/speech_acts this theory of speech acts was invented by J. L. Austin
in his book( How to do things with words)