Kaffarah is a form of compensation required when a fast in Ramadan is deliberately broken without a valid excuse, or when a serious oath is broken.
It carries a significantly higher obligation than Fidya.
As Mentioned in the Quran:
“Allah will not call you to account for your thoughtless oaths, but He will hold you accountable for deliberate oaths. The penalty for a broken oath is to feed ten poor people from what you normally feed your own family, or to clothe them, or to free a bondsperson. But if none of this is affordable, then you must fast three days. This is the penalty for breaking your oaths.”
Surah Al-Ma’idah (5:89)