What differentiates an off-grid inverter from a hybrid inverter considering that they both have the capability to connect to the grid?

An off grid inverter is a one-directional inverter (Power flows in a single direction – from the grid to the inverter – to either charge the battery or supply the loads). Whereas a hybrid inverter is a bi-directional inverter (Power flows in both directions on the AC side – from the grid to the inverter as well as from the inverter to the grid).

In essence, a hybrid inverter is capable of supplying grid connected loads (non-essential loads) using the renewable sources (solar and battery). On the other hand, the off-grid inverters can only supply essential loads. Moreover, hybrid inverters require the usage of energy meters/CTs to control the flow of power to the grid.