Coffee bags are simply tea bags with coffee. They contain whole coffee beans that have been finely ground before being added to the bag.
Coffee in a coffee bag is different from instant coffee because instant coffee completely dissolves when water is added.
Only 30% of the ground coffee will dissolve to create a cup of coffee and so keeping the other 70% inside the bag makes it easy to get rid of without creating a mess or the hassle of cleaning away the used coffee grounds.
Nothing beats a proper cuppa. It’s an easier way to brew proper coffee with no mess or fancy brewing equipment needed. Just boil the kettle and you’re good to go.