your laptop wifi is not good enough to see the 5ghz. that's all.
it's a new standard and limited to AC adapters if i recall right. perfectly normal. the 2.4 ghz, which is what your laptop is seeing, is a stronger signal and goes further but does not have the speed capabilities of 5 ghz. on the other hand while 5 ghz is faster, it's range is a lot less than the old 2.4 ghz.
unless you've got a GB connection, then the 2.4 ghz should be enough anyway to get all or most of the speed your paying for. so the 5 ghz is not really needed except for those with super fast access.
if you're losing sleep over it and want the 5 ghz on your laptop, then you'll need to upgrade the wifi card on the laptop or get a usb adapter to connect with. i use...