Help for understanding a jargon on PCB designing
What Ignacio answered is right. I like to add an example for you to understand this rule: Imagine a water tank and two houses with pipes connected to the tank. It is best if both houses have separate pipe connections to the (common) tank, because then they do not disturb each other. If one house has its pipes connected to the pipes of the other house, then they will affect each other when pulling water. E.g. the last house in the chain will not get any water if the first one pulls water, because the pipe capacity is used by the first house. Similar situation with electrical current.