This, above, is a flower bud on a Peach tree.
This, is a leaf bud. One will give you a Peach, the other will give you a leaf. Simple really. Ideally your Peach tree should be displaying some of each right now.
If any of your Peach branches do not have flower buds on them, just leaf buds, then it means that when you prune your tree at the end of the Summer you need to replace that branch with a younger one. You could tie a bit of coloured string round it now to remind you.
Peaches flower on last year’s wood. This can be a new whole branch or a spur (a stubby bit of new growth from an old branch). But they need new growth in order to produce flower buds.