This question is very generic as there are multiple types of nexus switches and they all vary in what they can do and some are built for specific models like stocks and trading for low latency , there data centre switches by design
https://en.wikipedia.org/wiki/Cisco_Nexus_switches
https://www.sdxcentral.com/cisco/datacenter/definitions/cisco-nexus-switch/
use nx-os software
Difference btw normal 3850 and nexus
huge difference in speed and features depending on model and size
Why it has ethernet ports
some have , some haven't , some a mix of fibre and copper again depending what your needs are in the data centre
