you can say that it is basically a whole copperlayer for ground (- power)
so if you need a - power in your design (ground) you just put a via (hole with a conductive area in it) to fish up the ground where you need it..
Yes, but the whole copper plane is not filled with copper, or is it (ie. it is not like a solid filled rectangle in a paint program)?
So the copper in the copper plane forms some islands/blobs or maybe better said some kind of trace maze. And I was wondering if on pcbs there is always just one single such trace maze/labyrinth (where you can get from every possible point in the maze to every other possible point on the maze) or whether there can be multiple ones which are not connected by themselves (no way to get from a point on maze #1 to a point from maze #2 because they are not connected). And it's only the installation of some pcb component which later will causes the mazes to be bridged, so that they end up being connected.
stupid example: if you had a circuit with a lamp and a fuse on the negative side then as long as the circuit is unpopulated then it would look like the ground connection from DC In to lamp ground pin is missing.
