A little bit more about Polygon
Polygon can be used for various purposes, for example: We can draw large signal areas by using it in any shape. or we can use it to fill the empty pcb area with copper, to make it look more professional. For 1 st purpose make a board in eagle, give name to the signal (as -ve in below fig). Now draw the poly gon (as i mentioned in my previous article) and give it the same name i.e., -ve. The result is like this: You can see the –ve signal and polygon merges together. For 2 nd option, just change the name of polygon (say Vcc) without changing the signal name. After doing this you will find this: Both the signals are separate. So, you can easily find the difference between these two.