What is the meaning of quatrains in ancient poetry?

1, the ancient poem "quatrains" means:

Two orioles sang tactfully among the green willows, and a group of neat egrets went straight into the blue sky. Sitting by the window, you can see the snow accumulated all the year round on Xiling Mountain, and ships from Dongwu, thousands of miles away, are parked in front of the door.

2. The original quatrains

Tang-Du Fu

Later that day, Jiang,

Spring breeze smells of flowers and plants.

Muddy swallows,

Sleeping mandarin ducks on the warm beach.