No difference , Its the same thing where a UE is simultaneously connected to two cells (one Macro , one small cell)
The Macro cell will use a different frequency (lower) than the frequency used by small cell (higher)
There are two variations here though :
1. Control signalling handled exclusively by Macro cell and Data/user plane handled exclusively by Small cell.
2. Control plane handled by macro or small cell and data plane divided between Macro and small cell.
Dual connectivity: Devices maintain simultaneous connections to both macro and small-cell low-power layers to improve cell-edge throughput. Inter-node radio resource aggregation can use radio resources on a common frequency in more than one eNodeB. In addition, connections can be anchored to a macro cell on one frequency while boosting data-rates via the small cell on a different frequency.