Sour Cherries (or tart cherries) are a sort of poor relative of best-known cherries, of which they taste much bitterer.
Their trees also differ: prunus cerasus, commonly called sour cherry tree, is much smaller.
There are two varieties of sour cherries: dark-red morello cherry and lighter-red amarelle cherry.
In cooking, you can use sour cherries to make great liquors. For example, maraschino, a Danish liqueur used to flavor ice creams and fruit salads. It is very simple to make. Just put whole (but washed) sour cherries in a container full with 90° alcohol, and let rest in a dark place for 2 months. Then, make a syrup with water and sugar (bring to a point of boil, then let cool down). Combine the two (the syrup with the sour cherries in alcohol). Let rest another 2 months, and that’s it.
Fun fact: their pits can be used to make pillows with therapeutic effects on cramping stomach, painful neck and similar. You need to wash them and let them dry with sun light for about 2 days. And fill your pillow. Whwn needed, just heat your sour cherry pit pillow for a couple of minutes in the microwave, and put it on the painful part.