A Domain Specific Language is optimized for performing tasks within a limited problem area. Usually the syntax is simplified to strip out features that dont pertain to the problem. Examples are shell scripting languages like bash or windows shell, awk, sed, SQL, HTML, TEX, or JSON. Imagine trying to typeset a document in raw java.

There used to be lots of little declarative DSLs. Think make. Now they have been co-opted by XML. Ant uses XML, but would be much prettier if it had its own DSL. Another example: you can hand code a parser, but it is much easier to code and debug, if you use BNF (YACC or Bison).