Dim sum, literally "touch your heart", is a Cantonese term for small hearty dishes.These bite-sized portions are prepared using traditional cooking methods such as frying, steaming, stewing and baking. It is designed so that one person may taste a variety of different dishes. Some of these may include rice rolls, lotus leaf rice, turnip cakes, buns,jiaozi-style dumplings, stir-fried green vegetables, congee porridge, soups, etc. The Cantonese style of dining, yum cha, combines the variety of dim sum dishes with the drinking of tea. Yum cha literally means 'drink tea'. -from wikipeda.org
My city shenzhen is a part of Guangdong which is canton, so of coures my families always go eat dim sum a lot. Usually we will go to a famous restaurant which has long history and have really authentic dim sum and we will go there in the early morning but always there will be more people go there more early than us. And usually all the restaurant will put all the dishes liked a mountain, then you just pick whatever you want.