The word meaning of tether is a rope or chain used to fasten animals. In space tethers have an application similar to their word meaning. Here we have satellites and spacecrafts instead of animals. A tether if connected between two space crafts (one having lower orbital altitude and the other at a larger orbital altitude) momentum exchange can take place between them. Then the tether is called a momentum exchange space tether. But tethers are being made of electrically conducting materials like aluminium or copper and they provide an additional advantage. They are called electrodynamic tethers. They can convert orbital energy into electrical energy. It works on the principle of electromagnetic induction. Also when the conductor moves through a magnetic field, charged particles in the conductor experience an electromagnetic force perpendicular to both the direction of motion and field. This can be used for power generation. This can be use for orbit raising or lowering, debris removal. Another application of tethers discussed here is artificial gravity inside space crafts.