Mugs aren't just big cups for tea, coffee, or hot chocolate. A mug is a statement in itself, an art form, something personalised and decorative. Mugs have slogans, photos, works of art, and other images, and come in many different sizes.
Mugs are ceramic usually but sometimes glass. A mug can be smallish and suitable for holding a serving of tea, or it can be pint sized for an extra-large drink. Drink it from a big mug.