Simply put: it’s a way of brewing coffee in cold water for a period of time (overnight is good).
It definitely has a few advantages over your regular cup of coffee. For one, the acidity is lowered so it has a much smoother flavour. This means it’s not only easier on your taste buds but on your stomach as well. Also it's versatile- you can enjoy it strained and served over ice or use as a base for a cocktail, an iced coffee, a shake or anything else you might fancy! Bonus: you can make a concentrated version and store it in airtight container in the fridge and it will be good for at least a week.