One question that comes up when using the Magic Wand tool is, "what do those pesky options mean?" Specifically, people get confused about Contiguous and what it does.
When it's selected, only the pixels that have the same colour value as the targeted area get selected. If it's not selected, then all pixels that have the same colour value are selected - no matter if they are interconnected or not.
It's really just an additional level of control for your Magic Wand tool.