Markers of identificational and explanatory clauses

Words that begin a clause that identifies a specific case or example of what has just been said, or that explains what has just been said.

• What words are used to identify a specific case?
  that namely namely that that is i.e.
• What words are used to introduce an example?
  for example e.g. as follows as below such as let me give you an example to illustrate
• What words are used to introduce an explanation?
  what I mean is that is to say let me add allow me to explain it's like
• What words are used to introduce a conclusion?
  which shows that so we find so we see
• What words mark a digression?
  let me just insert as an aside this is off the subject oh by the way