What do you mean by "national style" and "Song Ya is good" when satirizing four poems?

The meaning of this poem is: national style, elegance, Xiaoya and Fu, collectively called four poems, should be worth reciting.

The enlightenment of this poem is that The Book of Songs is the earliest collection of poems in China. * * * has collected more than 300 poems of the first Zhou Dynasty with a wide range of themes, some reflecting love, some reflecting war and some reflecting customs, which is a mirror of social life. Among them, irony is reading aloud. The Book of Songs is rich in content and life-oriented, so scholars should recite it frequently.