The twenty-four solar terms divide the ecliptic into equal arcs of fifteen degrees, and this one falls at 315 degrees of the sun's apparent longitude. It is a sectional term, a jie, one of the twelve that fall in the odd positions of the twenty-four and open the twelve solar months. The sectional terms and the major terms alternate strictly around the year, so a jie is always followed by a zhong fifteen degrees later.
The twelve major terms are what make the Chinese calendar work as a lunisolar one. Each ordinary lunar month is expected to contain exactly one major term, and the month takes its number from the term it contains, so the eleventh month is by definition the one holding the winter solstice. When a lunar month falls entirely between two major terms and contains none, it is declared intercalary and repeats the number of the month before it, which is how a thirteenth month is inserted without any fixed rule about when.
Lichun carries a weight the other sectional terms do not, because it, and not the lunar New Year, begins the year in the sexagenary reckoning used for fate calculation. A Four Pillars chart takes its year pillar from Lichun onward, so a birth in late January or early February can fall in one animal year by the festival calendar and the previous one by the astrological reckoning. Popular custom also treats a lunar year containing no Lichun as inauspicious for weddings, a belief that follows from the intercalation rule rather than from anything about the term itself.