MySQL - length() vs char_length()

What's the main difference between `length()` and `char_length()`? I believe it has something to do with binary and non-binary strings. Is there any practical reason to store strings as binary? mysql> select length('MySQL'), char_length('MySQL'); +-----------------+----------------------+ | length('MySQL') | char_length('MySQL') | +-----------------+----------------------+ | 5 | 5 | +-----------------+----------------------+ 1 row in set (0.01 sec)