What is the difference between Palindrome and Reverse function?

It is to be denoted that the words of PALINDROME are called palindromes.
Reverse (w) = w
e.g: Σ={a,b},
PALINDROME={Λ , a, b, aa, bb, aaa, aba, bab, bbb, …}
If a is a word in some language L, then reverse (a) is the same string of letters spelled backwards, called the reverse of a.
e.g reverse (xxx) = xxx
    reverse (623) = 326
    reverse (140) = 041