There are a number of words that are used to specify the capabilities and capacities of the various shredders that are available. Most of them make sense and need no explanation but it's helpful to have them all listed together for easy reference.
Cross cut: Shredders typically cut the paper into vertical strips (usually referred to as strip cutting). Cross-cutting means that the paper is sliced horizontally. All shredders strip-cut; adding cross-cutting means that the paper is cut both ways, into confetti-like particles that are much less bulky than strip-cut, and are much more secure in that it's going on impossible to reconstruct a document from them.
Feed opening or feed width: The width of the slot into which the paper is fed: minimum size is 9 inches, to accommodate the usual 8 1/2 x 11" letter-size paper. Can be as wide as 16".
Output: How many pounds of shredded paper per hour the shredder can produce.
Sheet capacity: How many sheets at a time the shredder can take in.
Shred size: The size of the shredded pieces: either just a width or a width and length.
Speed: The speed at which the sheets go through the shredder. Usually measured in feet per minute. This is of greater importance for use in shredding continuous forms.
Waste capacity: The volume of paper a waste bin or bag can accommodate, in gallons.Overload protection: Some paper shredders have a feature in which sensors will turn the shredder off if too much paper is inserted.
While the above terms describe the use to which the shredder can be put, physical specifications such as shipping weight and electrical power requirements may also be important. The warranty on the parts, especially for the more expensive models, comes into it as well. Finally, you may want to consider whether the shredder can cope with staples and paper clips, and whether it will be used for credit cards or even CDs.