SQL & PL/SQL

hi

what is difference between value clause and deref clause in object orient programming in plsql. i try to understand it from documentation but did succeed. here is my confusions

so times in oracle documentation i see an example like this

select value(i) into object_variable
from table i;

why value is used here if for getting value of the object then sometimes i see an example like this

selet i into object_variable
from table i

where i is an object. what am i missing here. please help