A mother is a female parent: mothers nurture and mother children. It's also a term for an elderly woman or mother superior.
Your mother is the woman who gave birth to you: mothers are parents, the female equivalent of a father. Besides biological mothers, there are stepmothers and adopted mothers: they all do mothering, which means taking care of children (or, sometimes, being overprotective of children). Oddly enough, a mother is also slimy substance that forms during the fermentation of wine or cider. But in any case, mothers give and sustain life.