A paper jam is a condition where paper gets caught somewhere in the printing mechanism of a printer, photocopier or fax machine. Typical causes of a paper jam include old or worn down parts, incorrect paper type, multiple pieces of paper stuck together, or high humidity, which can cause the paper to warp and cause a jam. The problem with paper jams is that they can occur at any time and cause a big issue if you're in the middle of printing a 100 page report.
Clearing a paper jam is a matter of opening up the device, locating the sheet of paper and removing it. While it may seem easy, it may be quite an undertaking depending on the complexity of the device. Fortunately, most modern devices have some sort of indicator to let you know where to start looking. Of course, if the issue is a worn part or sensor, the device may be throwing a false error. Most times removing the paper and resetting the device is all that's needed. If the jam occurs over and over, it may be time to get your device serviced. If you were printing a document from your computer, you may or may not need to resend your document to get it to print, but that depends on the printer and software you are using.
To prevent paper jams, make sure you're using the correct paper and perform proper maintenance on your device. Even with these steps, sometimes a jam will happen. For the most part, though, jams should be few and far between. If the frequency of jams goes up, check your device and optionally have it serviced.