xml - If double slash (//) is used 2 times in XPath, what does it mean?

Question

What does a double-slash used twice in an XPath selector mean?

Suppose I'm using a path like:

//div[@id='add']//span[@id=addone']

Answer 1

A double slash "//" means any descendant node of the current node in the HTML tree which matches the locator.

A single slash "/" means a node which is a direct child of the current.

//div[@id='add']//span[@id=addone'] will match:

<div id="add">
  <div>
    <span id="addone">
  </div>
</div>

And:

<div id="add">
    <span id="addone">
</div>

//div[@id='add']/span[@id=addone'] will match only the second HTML tree.