I asked Mr. Google who said
a cross between lemon, tangerine, and passionfruit. It is super tart with a slight floral finish.
This article suggests ways to use them, such as juicing and making marmalade:
They can be juiced, and their tart, aromatic juice is used to make a refreshing Philippine lemonade. The fresh juice can be mixed with other juices or even frozen to make ice cubes which are then added to iced tea, lemonade, or other beverages.
https://www.thespruceeats.com/what-are-calamansi-limes-5210037
If you find a good use for them, please let us know.