The Witches are preparing to cast a spell on Macbeth
"Double, double toil and trouble. Fire burn and cauldron bubble" (IV.i.20-21).
1st apparition Talking to Macbeth
"Macbeth! Macbeth! Macbeth! Beware Macduff beware the thane of Fife" (IV.i.78-80).
2nd Apparition that talks to Macbeth
"Be Bloody, bold and determined; laugh to scorn the power of man for no one born of woman shall harm Macbeth" (IV.i.87-89).
The witches are preparing to cast a spell to show Macbeth apparitions to show him the truth of the prophecies. These truths are going to drive Macbeth mad.
3rd apparition to talk to Macbeth
"Be Lion hearted, proud, and don't worry about who is irritated or discontented or where the plotters are. Macbeth shall never be defeated until great Birnam Wood Shall come against him at Dunsiname Hill" (IV.i.100-105).
The first apparition is telling Macbeth that he should be wary of Macduff foreshadowing that Macduff is gonna be the end of Macbeth himself
4th apparition to speak to Macbeth
"One by one, a possession of eight Kings appears. The last king carries a mirror in his hand. Banquo's ghost follows them" (IV.i) Banquo's ghost is showing that Macbeth will be overthrown no matter what he does which strikes fear into Macbeth's heart making him paranoid
This apparition is telling Macbeth that he cannot be harmed by any human since all humans are born of a woman only a mythical creature can harm Macbeth.
How the meeting with the witches Impacted Macbeth
"You shall not live, Macduff, so that I may despise my fear, and sleep through thunder" (IV.i.92-94)
This apparition is telling him not to worry about others because he is going to defeated eventually.
Macbeth meeting with the witches made him more arrogant and paranoid than he was and turned him into a tyrant. Macbeth then proceeded to send someone else to slaughter Macduff's family.