When an UE registers to the network first time, Network gets "Ue Radio Capability" information from UE as part of attach procedure and store it.
UE Radio Capability IE has a lots of information, some of the information is used by eNodeB.
I know that eNodeB uses the information received as form of UE Radio capability for the measurement and handover related stuff.
Feature group indicator carries some important information which may be required by MME. for example: How many AM and UM mode DRBs, UE supports.