Jeremy Keith and Brad Colbow explain the difference between the two markup languages in simple terms.
XHTML 2
Contrary to some beliefs, XHTML 2 does not have anything to do with XHTML 1.0 or XHTML 1.1. XHTML 1.0 is simply a reformulation of HTML 4 with XML syntax.
- lowercase tags and attribute names
- quoted attribute values
- mandatory closing tags for p and li elements
- a slash (terminator) at the end of standalone elements such as img, br and meta
XHTML 1.1 is the same reforumulation but requires that documents be served with an XML mime-type.