1) In a computer, a jumper is a pair of prongs that are electrical contact points set into the computer motherboard or an adapter card. When you set a jumper, you place a plug on the prongs that completes a contact. Jumper settings tell the computer how it is configured and what operations can be performed. Computers come with jumpers preset. Instructions are sometimes provided so that the owner can reset the jumpers when new equipment is added. The latest trend, however, is plug and play equipment that does not require manual setting of jumpers. A group of jumpers is sometimes called a jumper block.
Finding the right jumper settings for a particular computer configuration usually requires having some technical information that comes with each product for which a jumper setting has to be set or changed. Where this information isn't available, you may be able to find information at the Web site of the manufacturer.
2) In electronic test equipment, a jumper cable is used to make a temporary contact between two points for the purpose of testing a circuit.