A BLOB is a binary large object that can hold a variable amount of
data. The four BLOB types are TINYBLOB, BLOB, MEDIUMBLOB, and LONGBLOB.
These differ only in the maximum length of the values they can hold.
The four TEXT types are TINYTEXT, TEXT, MEDIUMTEXT, and LONGTEXT. These
correspond to the four BLOB types and have the same maximum lengths and
storage requirements. See
http://dev.mysql.com/doc/refman/5.1/en/storage-requirements.html.

URL: http://dev.mysql.com/doc/refman/5.1/en/blob.html

