calamondins are like tiny mandarins/tangerines, but fruits are more zesty instead of sweet, so used like lemons or limes. Calamondins are more cold-hardy than mandarins, i actually think it is only second to trifoliates, and an equal of kumquats in cold-tolerance
i posted photos of regular calamondin and variegated calamondin below. These have endured 20F winters outdoors and unprotected. The variegated calamondin seems to be tougher as it does not drop its fruits or foliage