What is the five-character seven-law?

Poetry is divided into ancient poetry and modern poetry. The number of words in ancient poetry is not uniform. Modern poetry is divided into five words and seven words, that is to say, the number of words in each poem is five words. Five words are divided into five rhymes and five quatrains, with a total of eight sentences. The quatrains are actually cut in half, leaving only four sentences. Five-character poems such as "Du Yue: Mount Tai is the top! Endless green spans Qilu and Qilu .. magical nature brings together thousands of beautiful mountains in the south and the separation between morning and dusk in the north. There are clouds in the soup chest, and birds fly back and forth in front of my nervous eyes. Once you climb to the top of the mountain and peek, you will see that other mountains look short under the sky ... "The five-character quatrains such as" Li Shangyin's amusement park scenic spot: there is a twilight shadow in my heart, and I have driven to the Leyou tomb. The sunset is infinitely beautiful and is buried by the coming night. " Seven-character poems are also divided into seven-character poems and seven-character quatrains, such as "Li Shangyin has no title: the time was long before I met her, but it was longer than after we parted. The east wind started and all flowers were exhausted. Silkworms in spring will weave until they die, and candles will drain the wick every night. In the morning, she saw her hair cloud changing in the mirror, but she bravely faced the cold of the moonlight with her evening song. It's not a long way to Pengshan. Oh, Bluebird, listen! -Give me what she said! "Seven-character quatrains such as" Du Mu Qingming: It rains a lot during Qingming Festival, and pedestrians on the road want to die. Excuse me, where is the restaurant? The shepherd boy refers to Xinghua Village. "