Let us say at the get go about weeds in a vegetable garden. THERE NEVER NEED EVER BE ANY WEEDS IF YOU MULCH 365 DAYS A YEAR!
Weeds are a problem because they compete with the vegetables we are growing. They use up nutrients. They take away water. And sometimes they bring an alleopathic effect that is chemically harmful to some vegetables. In short, we want no weeds in the vegetable garden.