Leaves are part of the aerial part of the plant consumed to nourish your body and soul. You can make herbal infusions with them, you can eat them, you can grind them up in your smoothies, you can put them in your soups and stews, you can eat them on a cracker. You can (for instance) use chickweed (or dandelion) in place of lettuce on a sandwich. You can steam them, boil them, (not advised LOL) and you can put them on top of your backed potato.
Joshua Engel says..
Leaves and stems are mostly identical in nutritional value. Stems can be tougher and harder to digest, and in some plants much of the stem isn’t edible and must be trimmed. (Broccoli, asparagus, and artichokes come to mind.) Leaves and stems are botanically very similar. Michael Pollan’s advice to eat “mostly leaves” would be better put as “mostly leafy plants”.
You can chew them up in your mouth (don’t swallow) and put them on a mosquito bite