A mug is a dish for holding a warm drink. A mug of your favorite warm drink can be very comforting.
a variety of mugs
Mugs can be made out of a variety of materials. The most common is probably ceramic. Others are made of glass, plastic or metal.
Some mugs are better insulated than others and will keep drinks hot or cold for a longer time. Some mugs are designed for travel. They have lids, so it is less likely that the liquid they contain will spill during a commute or other trip. The lids usually have a slot or small hole, so you can drink without removing the lid.
Most mugs have a handle, but some insulated travel mugs do not.
a collection of travel mugs (with lids)