[kicad-users] Zones what are they and why do i need them??

[acidb...@ymail.com]

Ive read the help Docs in PCBnew on zones,but i still don't get
what they are used for.
Are they just for placing v+ and gnd ?
Couldn't I just place vias or pins for v+ and gnd?
Should i just make 2 polygons, one for v+ and one for gnd?