AVR-Chat

I understand bitwise operations but I don't get the following code.

DDRB|= (7<<3)

I understand that this is to setup the direction for port B  BUT why
are we doing [what appears to be] 7 shifted to the left 3 times
instead of 56 decimal

Is this the same?

DDRB|= (56)

OR are we shifting just the 7th bit left three times?  I saw in the
ATmega8 datasheet that the DDR registers are 8 bit.  Can you shift bit
7 left 3 times?


Heres's another one:

PORTB=PORTB|(1<<DDB5)

Why wouldn't we just say?

PORTB=PORTB|(DDB5)

or

PORTB=PORTB|(32)

I am new to AVR and WinAVR.

Where can I learn this information?   [books /internet/ datasheeets]

Thank you for your inputs.

David