What is the relationship between early summer and summer solstice?

It doesn't matter. Early summer is the first solar term in summer, which indicates that summer is about to begin, and summer solstice is the starting point of summer. At this time, the summer has already passed half, so the early summer has nothing to do with the summer of the solstice. Twenty-four solar terms refer to 24 special festivals in the China lunar calendar, which are formulated according to the changes of the earth's position on the ecliptic, and each solar term corresponds to a certain position reached by the earth every movement 15 on the ecliptic.