Ideally you want to be no where near an opponent’s guard. you should be on the outside, looking to pass without getting tangled up.

However, this is not an ideal world and getting tangled up in a guard, will happen in a competitive match. 

Passing established guards, looks at what scenarios you can take when you’re tangled up in your opponent’s open guard, from how to establish your base, to how to nullify you opponent’s guard, to eventually passing it.