Most of the devices we refer to as jet packs are actually rocket packs, sometimes called rocket belts. The difference between a rocket and a jet is significant. A jet intakes air, compresses it with a turbine and pushes it out the back, mixing it with fuel and combusting it in the process. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.