“Take your son Isaac, your only one, whom you love, and go to the land of Moriah. There you shall offer him up as a holocaust on a height that I will point out to you.”
Feast days are ranked according to their importance. Solemnities are the most important (typically commemorating Jesus or Mary), followed by feasts. Usually, “feast” celebrates saints which I’ve assigned to their own category. There’s a bit of an overlap of feast vs Solemnity. For example, while Mary’s major day on January 1st is a solemnity, her birthday on September 8th is a feast.