What are the three visions seen by Macbeth in Macbeth?

In Macbeth, Macbeth and Lady Macbeth have been so affected by the witches' prophecies that claim that Macbeth will be king that they have taken matters into their own hands to ensure that those prophecies do indeed come true. Their scheming and Lady Macbeth's unfailing resolve have resulted in Duncan's death and Banquo's death. Lady Macbeth had no idea that Macbeth intended to kill Banquo but she still defends him and protects him when he is visited by Banquo's ghost and risks exposing their evil plan to everyone at the banquet. 

Macbeth is unsettled and feels that the only way to resolve his issues, especially as he is so deeply entrenched in realizing the prophecies, is by visiting the witches, or "Weird Sisters" again. Act IV, scene i, opens with the witches who are making potions and devising ways to trick Macbeth, having realized that he is indeed wicked but that he is also easily manipulated and eager for any information that will elevate his status and confirm that he is doing the right thing. He expects the witches to warn him of imminent danger so he can take relevant action. 

Macbeth demands that the witches provide him with answers.

1. The first apparition appears. It is an "armed head" which warns Macbeth of the threat from Macduff. Macbeth thanks it but can glean no more information from it.


2. The second apparition is "a Bloody child" who tells Macbeth that "none of woman born" (80) will hurt him. This gives him confidence because, as everyone is born that way, he must be invincible.


3. The third apparition is "a Child Crowned, with a tree in his hand" who tells Macbeth that he cannot be defeated "Until Great Birnam Wood to high Dunsinane Hill Shall come against him." Macbeth is now so sure that he does not stop to consider any of the images beyond their face value.  

The only thing that still worries Macbeth that the witches have not yet answered regards Banquo's heirs. "A Show of eight kings" is then presented to Macbeth representing Banquo's line. Macbeth, however, will not let this stop him. He knows he is invincible and that will therefore secure his place even though he will apparently have no heirs of his own.