Home and office paper shredders can be designed to cut sheets into different shapes and sizes: strips, cross-cut, and micro-cut.
Strip-cut shredders cut sheets into strips. This offers a lower level of security, since anyone with enough time on their hands can tape the strips back together.
Cross-cut shredders reduce paper to much smaller pieces. Cross-cut is better than strip-cut in terms of security. Typically, this cut can suffice, though the pieces can still be put back together with a great amount of time and effort.
Micro-cut shredders reduce paper to pieces the size of confetti. It will be near-impossible to put the pieces back together. Thus, micro-cut shredders offer the highest level of security.