What's "Ethnography of Communication?"What's the difference between : Speech situtation;Speech event; Speech act?

The study of Ethnography of Communication includes a

description and analysis of speech habits, situational contexts, and cultural norms used in producing and evaluating speech.  It identifies the possible components, functions, and contexts of speech acts in a given speech community or society, as well as similarly delineating named speech events and speech situations in that community.

This includes: discourse, defined as utterance, communicative events and messages with linguistic meaning.  It also includes the Speech act, the minimal act employing verbal meanings like telling a joke.  You need a sender, receiver, message form, message channel, code, topic, and context.  There is also a Speech Event involved.  This is made up of one or more speech acts which have specific rules to control the use of speech.  An example would be a joke that might occur in a lecture or some other formal speech event.  Then there is the Speech Situation. Again, sticking with the same theme, a joke could also be told in a conversation, which is a speech event at a party which would be a speech situation.