mode=pages displays only the pages in the category; mode=all displays subcategories, pages and images; mode=parents displays only the parent categories; mode is categories by default.
depth=1 displays one level of the tree; depth=2 displays two levels of the tree, and so forth; depth is 0 by default.
hideroot=on hides the root category; hideroot is off by default.
showcount=off disables the (category, page, file) count after each category in the tree; showcount is on by default.
header=a user-defined header to override the default, for example "click + to show pages"