What is the direct object? - the sandwich

Who received the sandwich? - the man

What is the indirect object? - the man

"the man" is the indirect object because it tells us who the sandwich was given to.

The direct object is not always stated; in some cases it is implied.

Example:

My girl friend writes me every day.

What is the direct object? - letter (implied)

Who received the letter? - me

What is the indirect object? - me

"me" is the indirect object because it tells us who the letter was written for.

Example:

They told her.

What is the direct object? - it (implied)

Who received the action? - her

What is the indirect object? - her

"her" is the indirect object because it tells us who they told "it" to.