What does the 'alt' button can reveal when the computer doesn't really turn on?

[igmolinav]

Hi,

I remember long time ago that if the computer didn't turn on,
something to try would be to to press the 'alt' button at the
moment the computer was being turned on, this would be
done by pressing the 'power' button.

I have done so and I also stuck a USB stick to the USB port.

It gave me the option of choosing any of the two hard
drives, the internal or the USB stick.

I chose the internal hd first, and then the computer asked
me to choose an internet connection. I chose the internet
connection and waited for some ten minutes, but nothing.

I chose then the USB stick, and then the computer asked
me to choose an internet connection. I chose the internet
connection again and waited for some ten minutes, but
also nothing.

I did this procedure because I turned on an 11" MBA, and
the problem came when two to three seconds right after
the little apple came out, the computer turned itself off.
This happened every time I tried to turn the computer on.
I did it for four times. After this, I tried the above
mentioned procedure with the 'alt' key, but nothing
happened that could fix the computer and bring it back
to the good state it was before!

Would you have any idea about what may be going on
with this 11" MBA?

Thank you in advance, kind regards!