What do description, curtain and presence mean in calligraphy?

Draw, draw red. Give you a word on a red background and write it directly with a pen. Ordinary beginners. Copy, cover a piece of rice paper, write, and it's almost a description. Advanced. Dear, one side is copybook, and the other side is rice paper. Write according to the copybook and referring to the frame structure. Suitable for people who have no bamboo in their hearts. These three are from easy to difficult.