A data type for all features

You can use ST_Geometry when you are not sure which of the other data types to use.

Because ST_Geometry is the root of the hierarchy to which the other data types belong, an ST_Geometry column can contain the same kinds of data items that columns of the other data types can contain. Some visualization tools do not support ST_Geometry columns, but only columns to which a proper subtype of ST_Geometry has been assigned.