I have worked as both a kitchen salesman and a fitter in the past so will try to answer as best I can (it may get a little confusing so hold on!) Integrated appliance simply means that it is hidden behind a solid door, There is no difference in the workings of the fridge, the only thing stopping you using a normal fridge is the slight difference in depth and the fittings to attach the door to. An integrated appliance does not sit in a cupboard but is, in fact, free standing. it appears to be in a cupboard because of the door front. The difference in depth is only the thickness of the door as a normal fridge would sit flush with the other units and an integrated fridge has to sit slightly further back so the 'door' is flush.
Hope this helps :-)