What's the difference between the autumnal equinox and beginning of autumn?

Beginning of autumn is the beginning of autumn.

Beginning of autumn means that summer is coming and autumn is coming. Beginning of autumn is a transitional solar term, with the weather changing from hot to cold, and then from cold to cold.

Beginning of autumn is also called autumn, and the general trend is that the weather is getting colder. Due to the different climates in different parts of the country, the start time of autumn is also inconsistent. After beginning of autumn, early rice harvesting and late rice transplanting in central China, autumn crops entered an important growth and development period. Autumn means that summer is cool and autumn begins. The ancients regarded beginning of autumn as an important moment at the turn of summer and autumn, and always attached great importance to this solar term.

In ancient China, beginning of autumn was divided into three periods: one was cool wind, the other was dew, and the third was cold.