I see alot of advice on planting companions right next to your veggies, like basil next to tomatoes, for example. but then there's so much emphasis on weeding your garden ebcause weed will compete with your veggies and steal nutrients... So my question is, why are companion plants ok right enxt to your veggies? Won't they too compete with nutrients?

That's one reason to interplant, but there are others, such as planting something as a pest repellant or trap. Naturtiums, for example, are loved by aphids, so the aphids will go to nasturtiums planted near other plants, and protect them. If all goes well, ladybug larvae will come in to feast on the hordes of aphids. Quite a sight to see!

There's a great book called "Carrots Love Tomatoes" that goes into this in great detail, specifically naming which plants to plant with which others, and why.