Let me try to explain one by one -
Intra-frequency handover: UE remains on the same LTE channel and merely moves to another cell on the same frequency.
Inter-frequency handover: UE moves to a different LTE channel; an operator may have multiple LTE channels in the same area in order to serve high traffic demands.
Intra-ENB handover: When UE moves between cells managed by the same eNB. (Which is an intra-frequency handover) it is a case of intra-eNB handover.
Inter-ENB handover: Handover between two enodeB for whatever reason.
