The Cell Reselection concept is related to UE moving from one cell site (eNB) to another cell site (eNB) due to better signal strength criteria of target eNB when UE is in idle mode.
To keep it simple, Handover happens from source cell to target cell because target cell signal strength is better than source cell and HO condition met in connected mode. If this happens in UE idle mode, it will be cell reselection.
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