What is a dependant claim?

In a patent or patent application, the claim is the precise legal definition of the invention, identifying the specific elements of the invention for which the inventor is claiming rights and seeking protection. There are two types of claims. One is an independent claim and the other is a dependent claim. While an independent claim does not refer to or rely upon any other claims in the patent, a dependent claim specifically refers to and relies upon another claim. 
For example, suppose Claim 1 in a patent for a pencil starts out, in legalese, as “a device comprising a cylindrical piece of wood with a piece of lead inserted into the center of the wood….”  That’s an independent claim. Meanwhile, if Claim 2 is a dependent claim for the same pencil with an eraser, it might start, in legalese, as “a device as described in Claim 1, wherein a piece of rubber is attached to one end of the cylindrical piece of wood….”