What is difference between Cisco Nexus Switches and normal Catalyst switches?

catalyst switch as well as nexus switch both are switch so the basic behavior of both of them i.e transiting traffic over the network by switching at layer two . 

but there are loads of difference too because both switches as of different lineage 

one is used in small to medium enterprises lan where as nexus switches are used in data center lan . 

physically both have huge difference like memory , processor , back plane , control plane 

and logically nexus switches have advance features like vPC , otv, fabric-path but they are of no use in a small to medium enterprises lan  due to huge amount of differences in the  traffic  they process