During validation the CDATA XML Sections are ignored by the XML parser, so that you can place your code with special characters or non valid html inside that section.

The parser parsed the whole contains because XML elements can contain other elements, as in this example, where the element contains two other elements (first and last):

If you want to place a character like < OR > inside an XML element, it will generate an error because the parser interprets it as the start of a new element & end of element. You cannot write something like this:

To avoid this, you have to replace the "<" character with an entity reference, like this:

Note: Only characters like "<" and "&" are strictly illegal in XML. Apostrophes, quotation marks and greater than signs are optional, but it is a good habit to replace them.