Concept XML XLST preceding-sibling and ancestor

Question

I am very new to xslt, and found it can be easy or complex. I want to make clear some concepts. What is preceding-sibling and what is ancestor, after searching from google,

Answer 1

Preceding-sibling gets all element siblings that preceded it in the current node level. Unless you specify one or more of those preceding siblings with an xpath expression. If you specify a specific preceding-sibling with xpath it always starts with 1 in square brackets.

Ancestor is the first matching ancestor that matches the expression. So it goes back up the node tree to look at a matching expression based on where you currently are pointing. So if you were at product/inventory/drink/pop or just /pop then ancestor inventory/totalprice just looks for the frist occurence and it should only return back a pointer to point to that matching case else it will be pointing to nothing and you'll still be pointing at pop.