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)