I am by no means a networking guru, but I do work in the IT industry so I know some things more than the average person.
One good example is this – If you connect to your wireless router at 300mbps, it does NOT mean you will get 300 mbps speed. It means you can get “up to” 300 mbps, best case. Real life situations often cut this speed by 50% or more. Why? Because of all the electromagnetic signals being generated by everything around you – your phone, your TV (worse still if CRT TV), fridge, microwave etc.