What are the meaning of XI, PI and BI?
I am new in this world and I am trying to understand basics concept, but I cannot understand the meaning of these "XI" "BI" and "PI" (and I don't know if I am missing some of them!). I cannot understand what are these? I don't mean what they do, or their capabilities ... I mean: what is XI (PI BI)? is a component ? are they modules? are they versions? are they connected? If I have one of them can I have one more ? can I upgrade one to one other?
I know it's impossible to answer to this question in a post ... I am looking for a document that explains an overview on this concept I would like to understand.
Thanks in advance.