Stripping wire is a first step to building an electrical cable or any other electrical connection. Wire almost always has insulation around it to keep the wires from getting crossed. To make a connection between two wires one must join them together, or attach connectors to them and attach the connectors together. The first step is to prepare the ends of the wires by stripping off the insulation.
It's best to use a wire stripper .. these come in many forms but they are shaped similarly to scissors. However they are not meant to cut all the way through a wire and instead there will be half-circles cut into the the edge of the blade. The half circles match the gauge of the wire (thickness).
To strip insulation from 10 gauge wire, use the half-circle which is labeled "10". Same for 12 gauge wire or whatever wire size you have. The size of this half circle is just right so to cut the insulation without cutting the wire inside.
Wire strippers usually also are wire cutters.
For thick wire there are special wire strippers which are shaped differently and used in a different way.