What are the special characters in XML?

If you use XML with no DTD, then these five character entities are assumed to be pre declared, and you can use them without declaring them:

<
The less-than character (<) starts element markup (the first character of a start-tag or an end-tag).

&amp;
The ampersand character (&) starts entity markup (the first character of a character entity reference).

&gt;
The greater-than character (>) ends a start-tag or an end-tag.

&quot;
The double-quote character (") can be symbolized with this character entity reference when you need to embed a double-quote inside a string which is already double-quoted.

&apos;
The apostrophe or single-quote character (') can be symbolized with this character entity reference when you need to embed a single-quote or apostrophe inside a string which is already single-quoted.

If you are using a DTD then you must declare all the character entities you need to use (if any), including any of the five above that you plan on using (they cease to be pre declared if you use a DTD). If you are using a Schema, you must use the numeric form for all except the five above because Schemas have no way to make character entity declarations.