This field controls the number of columns.
The search term searches the title field for whatever string you enter. One possible use is to search for all the cassettes of a particular series. Eg: Search for "HG50" and you see that there are 8,9,and 10 speed himano HG50 cassettes.
Sort the results according to various fields. Some sort orders such as "Speeds" will do a secondary sort on Cost. Eg: If you look for 8 speed, you see the cheapest ones first.
Use this to see just a list of the cassettes with a certain number of speeds. Eg: All the 8 speed cassettes.
Availability Level. Use this filter to get a list of the readily available cassettes. It seems that Shimano website only lists the specs for their latest models. Eg: They have a page for HG50-8 but not HG50-7. But numerous websites list the HG50-7.