PCB Design - dashed lines on layers
The dotted lines form an area, in eagle called a polygon, to form a copper pour. This means the area within the dotted lines will be filled with copper (actually: the copper will not be removed from this area when the pcb is fabricated).
All traces crossing the area within the dotted lines will be surrounded by an open space so the traces will not be connected to the copper pour. 

These copper pours are often found as ground plane or, as the red dotted line in the bottom picture, as heat conductor. The red copper pour in the bottom picture, together with the via, will create an area where heat can be dissipated. 

As for the top picture, I don't know the benefit for the odd shape of the copper pour.

See picture for more info: