Double, double toil and trouble; Fire burn, and couldron bubble.
Call 'em. Let me see 'em.
Macbeth! Macbeth! Macbeth! Beware Macduff!
In the beginning of Scene 1 the three witches are casting a spell for someone. From them saying "toil and trouble" in their chant, it is assumed that they are creating this spell for Macbeth.
The power of man, for none of woman bornShall harm Macbeth.
Macbeth enters the cave to talk with the the witches. He wants them to set a storm and do the things that are needed so they will tell him his future. The witches ask if Macbeth would rather hear it from their masters. So Macbeth tells the witches to call them.
Macbeth shall never vanquished be until Great Birnam Wood to high Dunsinane Hill Shall come against him.
The witches summoned the demons/apparations. The first apparation, an armed head, tells Macbeth to beware of Macduff.
'Tis two or three, my lord, that bring you word Macduff is fled to England.
Fled to England?
The second apparition, a bloody child, tells Macbeth that no man born of a woman (meaning everyone) would hurt him. However that isn't including things not born of a woman, perhaps the apparations/witches.
The third apparition, a child crowned, with a tree in his hand, says to Macbeth to take courage, and that he wouldn't be defeated unless Birnam Wood traveled the 12 mile distance to Dunsinane Hill (Macbeth's castle).
After the three witches leave the cave, Lennox enters. He informs Macbeth about how Macduff has fled to England.