A palindrome reads the same forwards and backwards. "Racecar", "madam", even "A man, a plan, a canal: Panama" if you ignore punctuation.
Are They Actually Useful?
Not really, in a practical sense. But they're fun! And palindrome checkers are a classic programming exercise, which is why most converter sites have one.
I've shown the palindrome checker to kids who always get a kick out of finding new palindromes. Sometimes tech is just about having fun!