How does lucene index documents?

Question

I read some document about Lucene; also I read the document in this link (http://lucene.sourceforge.net/talks/pisa).

I don\'t really understand how Lucene indexes do

Answer 1

It is inverted index, but that does not specify which structure it uses. Index format in lucene has complete information.
Start with 'Summary of File Extensions'.

You'll first notice that it talks about various different indexes. As far as I could notice none of these use strictly speaking a B-tree, but there are similarities - the above structures do resemble trees.