What is the difference between grid station and substation?

Power substation steps down transmission level voltages (such as 66,132 KV) to distribution level voltages (such as 11 KV). A substation may have one or more step-down transformers and it connects a consumer to the network.

Power Grid Station is an interconnection point between two transmission line circuits (Rings), those are serving/connecting two geographic regions. Power Grid Station has transformer depending on the possibly different voltages, so that the voltage levels can be adjusted as needed.

Generally the substation is meant to distribute power supply. If the substation functioning with distribution of various voltage level (eg. 400/220/132/66kV), the same to called specifically as GRID SUBSTATION.