XQuery Basics

I want to visually see where the following 8 items below exists:

XQuery returns sequences like:                                                      Examples:
1- Atomic values; sequence can include atomic val.                   1.  Is this like number 3?  
2- Complex values (XML nodes).                                                    2. Are nodes <root>, <a> etc?
3- Element,                                                                                         3. Are a, b, c, d elements?
4- Attribute,                                                                                        4. I guess none given here.??
5- Text,                                                                                                5. I guess none given here.??
6- Processing instruction,                                                                6. n/a ??
7- Comment, or                                                                                 7. n/a ??
8- Document,                                                                                     8. n/a ??

In the following example:

DECLARE @x AS XML;
SET @x=N'
<root>
<a>1<c>3</c><d>4</d></a>
<b>2</b>
</root>';
SELECT
@x.query('*') AS Complete_Sequence, 
@x.query('data(*)') AS Complete_Data,
@x.query('data(root/a/c)') AS Element_c_Data;

Complete_Sequence                                Complete_Data     Element_c_Data
<root><a>1<c>3</c><d>4</d></a><b>2</b></root>       1342            3

Select allOpen in new window

I have plenty of links to read through. After reading the links, the above items are questions I have. There will be a follow up question requesting a better example so I could see all of the 8 items listed above.