There are three broad categories of materials available. Standalone Lessons, Courses and Collections. You can use the Material Type drop down menu to limit your searches to a single type of material, or you can include everything available on the site with the Any option. Selecting Any may prove useful if you wish to access Modules or Lessons within Courses, which otherwise cannot be searched for outside of the Courses which contain them.
If you select the Any option, some of the search parameters presented will not apply to every item since Standalone Lessons, Courses and Collections have different characteristics. As you select one of these options, the search parameters presented will be limited to the applicable options in each case.