What is the difference between .// and //* in XPath?

Question

While finding the relative XPath via Firebug : it creates like

1. .//*[@id=\'Passwd\']--------- what if we dont use dot at the start what it sign

Answer 1

1. For the first question: It's all about the context. You can see Syntax to know what '.', '..' etc means. Also, I bet you won't find any explanation better than This Link.
2. Simplified answer for second question: You would generally find nodes using the html tags like td, a, li, div etc. But '*' means, find any tag that match your given property. It's mostly used when you are sure about a given property but not about that tag in which the element might come with, like suppose I want a list of all elements with ID 'xyz' be it in any tag.

Hope it helps :)