Diary...Blog??

Diary and blog any differ??AS i know Diary is used for writing down our personal secret without let anyone know it..but nowaday blog maybe replace de diary with record down daily life with wat u see,who u meet,wat u wanna share to friends..i still remember one diary in my hometown in somewhr..so whr is it..i maybe forget oledi..maybe someone oledi read through tis diary although having the password to lock it but blog have any differ ??