Why is the word ‘concupiscence’ so important in understanding the difference between a Catholic view and a Protestant view of ‘Original Sin’?

I have noticed this word ‘concupiscence’ a lot while studying Catholic Theology. It seems to significantly change what ‘Original Sin’ means, making a Catholic meaning of ‘Original Sin’ very different from the Protestant meaning. It appears to be a key word because the Catholic Church actually condemned the Protestant view during the reformation as being heretical. A lot of it seems to boil down to the word ‘concupiscence’. I have not encountered the word a lot in Protestant theology but it is coming up left, right and center, as I study Catholic Theology. **Why is the word ‘concupiscence’ so important in understanding the difference between a Catholic view and a Protestant view of ‘Original Sin’?**