OBJECTIVE - G.CO.B.6
Use geometric descriptions of rigid motions to transform figures and to predict the effect of a given rigid motion on a given figure; given two figures, use the definition of congruence in terms of rigid motions to decide if they are congruent.
INTERPRETATION OF OBJECTIVE - G.CO.B.6
This particular objective connects isometric transformations to congruence. So this is where isometric gets put away and we start to use congruence. This is a major difference, that congruence is being defined as a single or sequence of transformations that map one onto the other.
This is the setup for determining the congruence between any two figures.
I think the 'predict the effect' phrase refers to understanding the coordinate rules for the transformations and predicting the transformation based on the rule.