1) Tree-based API: It compiles an XML document in a tree like structure and loads it into the memory. You can traverse and change the tree structure. Tree based API's are useful for a wide range of applications. Example of tree-based API is DOM parser.
2) Event-based API: An event based API provides the reports to an application about the parsing event. It uses a set of built-in call back functions. Example of event-based API is SAX parser.