@stu8 

Hey

Pretty easy one this, details below

OUTDOOR  -  The outdoor model has an antenna known as Omni-Directional which is the most common single straight pole type antenna.  Its radiation pattern is like a doughnut from the antenna, even in all directions radiating outwards.    Its designed to be placed in the centre of an open space with clients all round it in all directions.  Placing these against a wall or ceiling is a waste as 50% of the signal will blast straight into the brick..

INDOOR  -  Its a more focused antenna pattern, it radiates out from the white face of the AP at an 80degree angle   /  \  like that, so if its mounted on a ceiling anything above gets virtually no signal (by design, no point blasting into brick wall /ceiling), sides and below get the most signal.   My engineers always called these "claymore" type APs if that makes sense, face towards customers :)

Hope that helps!