How is the solar calendar different from the lunar?

The whole point is that the solar calendar is based on the days of the equinox and solstice. Thus, the year is divided into months (some are only winter and some are only summer). That is, in this case, the astronomical year is exactly observed. At the same time, the months are of different lengths.
With the lunar calendar, the lunar phases are taken as a basis. The essence of this calendar is that all of its months are of equal length.