Lemon Balm is a Mint family Herb. It is used to make a tasty tea with medicinal qualities. Folk Lore assigns many qualities to Lemon Balm. Science verifies some.
Medicinal Properties of Lemon Balm
Lemon balm has been used to soothe tooth aches and earaches, ease tension, headaches and high blood pressure, to dress wounds, for acne and boils, to treat herpes, bronchial inflammation, flatulence, influenza, morning sickness and relief from PMS.
I tried some on my wife for the latter of those claimed attributes, it didn't work much to my dismay.
Major components and compounds found in Lemon Balm include hydroxycinnamic acids such as rosmarinic acid and Caffeic acids. Chlorogenic acid, metrilic acid, tannins and assorted flavonoids which include luteolin, glucopyranoside and apigenin.
Hydroxycinnamic acids are Phytochemicals and have multiple health benefits as well as being helpful against a number of ailments. They have Antioxidant properties, promote lung health, help prevent and treat certain cancers, tuberculosis, diabetes and Malaria. They have anti inflammatory properties, Allergy-preventive qualities. 
Caffeic acids, much like the caffeine found in that cup of java, have been demonstrated to improve cognition and temperament. In lemon Balm, its interactions are believed to enhance cognition, mental acuity functions such as concentration, memory, alertness. It is proven that Lemon Balm Stimulates Acetylcholine Receptors.
It has produced favorable results in some studies in that it greatly increased the ability to perform word and image association tasks. One study in the UK students were found to be calmer, less stressed and performed better on multiple tests for up to six hours. 
Lemon Balm Tea Recipes
To make a simple Lemon Balm Tea it is best to use fresh leaves. Dried Lemon Balm leaves loose much of their flavor. Fill a glass jar to the rim with loosely packed fresh leaves, you want to leave ample air space within the leaves. Pour simmering hot water over the leaves before covering it to allow it to steep for about 10 minutes. Covering it is advisable in order to retain much of the vapors, which will resettle into the tea. Strain and then Enhance with honey, sugar, lavender sugar or stevia. It can also be drank without sweeteners.
You might prefer to make an iced tea version by chilling the tea. I like to make some ice cubes from one batch of tea to add to the next.
To make a sun tea Fill a jar in the same fashion as described above with fresh lemon balm leaves, I like to add a lemon wedge. Pour in cold water until it reaches the brim and allow it to sit in the warmth of the Sun for several hours.
Infusion process which works well with fresh, as well as dried herbs. Bring water to a boil, add 1 teaspoon of your dried ingredient per cup- - seep it in the water to allow the flavor to permeate the liquid. If you're getting into herbal teas you might want to consider getting a mesh ball - basically a metal tea bag.
Another method of making an infusion is to add a cup of dried herbs to a quart jar. Pour boiling water over the herbs to the top of the jar. You should also place a metal spoon or utensil in the jar when you are pouring the hot water if you are using glass. The metal will absorb the sudden heat and prevent the glass from shattering. Remove the metal utensil and cover the jar tightly with a lid. Let the herbs steep up to 10 hours and then strain.
References / Footnotes
1. Modulation of mood and cognitive performance following acute administration of single doses of Melissa officinalis (Lemon balm) with human CNS nicotinic and muscarinic receptor-binding properties.
2. Phytochemicals: 12 Health Benefits of Hydroxycinnamic Acids