Here is some jargon:
<price>19.50</price>
is called an
element.
It is introduced by a
start tag.
In this example, the start tag is:
<price>
And it is terminated by an
end tag:
</price>
A start tag may have one or more
attributes
as in:
<price units="pounds" country="UK">19.50</price>
An element may be
empty
as in:
<price amount="19.50"></price>
and this can be abbreviated to:
<price amount="19.50"/>
Another example is:
<unknown_price></unknown_price>
and this can be abbreviated to:
<unknown_price/>