I read Sutton's RL book and I found that in page 333
Although the REINFORCE-with-baseline method learns both a policy and a state-value function, we do not consider it to be an actor–critic method because its state-value function is used only as a baseline, not as a critic. That is, it is not used for bootstrapping (updating the value estimate for a state from the estimated values of subsequent states), but only as a baseline for the state whose estimate is being updated.
And the pseudo code of actor-critic is
In the above pseudo code, how can I understand bootstrapping, and I think REINFORCE-with-baseline and actor-critic are similar and it is hard for beginners to tell apart.