I this Scene, we see how Macbeth pays the witches a visit to kind of ask them about the future. The witches as representatives of evil obviously agreed to what Macbeth has asked them to do. The witches decided to give him apparitions. The first Apparition was an armed head, and he said that Macbeth needs to be careful of Macduff (the thane of fife).

FIRST APPARITION

Macbeth! Macbeth! Macbeth! Beware Macduff.
Beware the thane of Fife. Dismiss me. Enough.
The second apparition was a bloody child, and he told Macbeth that no one who is born from a  women can harm him (just a point, a surgery does not count).

SECOND APPARITION

Be bloody, bold, and resolute. Laugh to scorn
The power of man, for none of woman born
Shall harm Macbeth.
The third apparition was a child crowned, with a tree in his hand, and he told Macbeth that the end will be when the Great Birnam Wood to high Dunsinane Hill forest comes near his castle.
THIRD APPARITION

Be lion-mettled, proud, and take no care
Who chafes, who frets, or where conspirers are.
Macbeth shall never vanquished be until
Great Birnam Wood to high Dunsinane Hill
Shall come against him.
The fourth apparition was a display of eight kings that looked like Banquo and his sons, Macbeth obviously disliked that and started getting frustrated.
A show of eight kings, the last with a glass in his hand, followed by BANQUO
MACBETH

Thou art too like the spirit of Banquo. Down!
Thy crown does sear mine eyeballs. And thy hair,
Thou other gold-bound brow, is like the first.
A third is like the former.—Filthy hags!
Why do you show me this? A fourth? Start, eyes!
What, will the line stretch out to th’ crack of doom?
Another yet? A seventh? I’ll see no more.
And yet the eighth appears, who bears a glass
Which shows me many more, and some I see
That twofold balls and treble scepters carry.
Horrible sight! Now I see ’tis true;
For the blood-boltered Banquo smiles upon me
And points at them for his.
He then asks if Lennox has seen some weird girls, and wished upon all the people that trust them hell. (Including himself!)