[NTLUG:Discuss] slightly off topic - external monitor for linux laptop

[Fred James]

All
If I hook a monitor to the video out (15 pin) on my laptop, the screen 
shows up there too - right?
If that monitor is big (as in bigger than the one on the laptop) the 
image on it is a magnified version of the image on the laptop screen - 
right?
If that's all correct so far - any gotcha's I should look out for? - 
will any monitor do, or is it band and model specific?
Thank you in advance for any help you may be able to offer
Regards
Fred James