p2 repository creation ant tasks like eclipse.publish.featuresAndBundles seem to take a site.xml or category.xml file which specifies the category information.
I see that the contents of site.xml and category.xml that eclipse generates are exactly the same right down to the tags.
So what is the difference between the two?
Edit - To be clear :
What additions/subtractions are present in category.xml that differentiate it from a site.xml apart from the filenames?
The main difference between the to that the site.xml provides information where the update site and other repo information can be structured, and it is part of the update site, but as of 3.4 it has been replaced with content.xml and artifacts.xml
In the categories is an XML file describing categories, it can be consumed during a p2 build and produces the categories seen in the Help>Install New Software dialog. But again with p2, categories.xml can be replaced with a child repo in a composite repo containing the information you would expect.
来源：https://stackoverflow.com/questions/4945466/eclipse-p2-difference-between-category-xml-and-site-xml