They are the witches that give Macbeth and Banquo prophecies. They are basically the cause of the whole story.
The three witches
Banquo is referring to potential dangers or consequences that may stem from Macbeth's sudden rise to power, suggesting that it could have come from a dangerous or unpredictable source. He is indicating his suspicion that the weird sisters and their prophecies may have played a role in Macbeth's transformation.
"All hail Macbeth, hail to thee, Thane of Glamis" - what he already is "All hail Macbeth, hail to thee, Thane of Cawdor" - who lives "All hail Macbeth, that shalt be King herafter" and for Banquo they said his children will be kings
Banquo: I dreamt last night of the three weird sisters. To you they have shown some truth. Macbeth: I think not of them.
Macbeth is most worried about the prophecy that Banquo's descendants will inherit the throne, as he fears losing his own grip on power and authority. This thought fuels his paranoia and leads to his decision to have Banquo and his son killed.
That his crown will not go to his decedents, but instead will give his crown to Banquo's sons and grandsons. Banquo decides to go to the ceremonial banquet.
they had beards.
Banquo says, in Macbeth, "I dreamt last night of the three weird sisters. To you they have shown some truth."
He dreamed of the three witches, and then confided in Macbeth about his dreams. Macbeth replied that he hadn't thought of the three weird sister, which was a lie.
In Act 2 Scene 1 of the Shakespearean play 'Macbeth', Banquo and his son Fleance met in the court of Macbeth's castle at Inverness. Banquo explained that he had been unable to sleep. He said that 'cursed thoughts' [Line 8] were keeping him awake. Most likely, he was referring to the witches' predictions of his fathering a long line of kings of Scotland, in Act 1 Scene 2.
In Shakespeare's play "Macbeth," Banquo describes the witches as having beards and choppy fingers, which are physical features typically associated with men. These features contribute to the witches' eerie and unnatural appearance, leading Banquo to question their gender.
Macbeth takes them more seriously than Banquo. There is nothing Banquo could do anyway to make his children become kings without him becoming a king himself. But Banquo, despite his lighthearted reaction to the witches, does not forget them. In Act II Scene 1 he says to Macbeth, "I dreamt last night of the three weird sisters. To you they have shown some truth." So perhaps there is not such a difference between their reactions after all.The difference between the witches' predictions for Macbeth and those for Banquo are that the ones for Macbeth are being fulfilled even as they speak, whereas Banquo's will not happen in his lifetime. There is no incentive for Banquo to try to hurry them on; there is such an incentive for Macbeth. It is this and not their reactions which send Macbeth and Banquo down separate paths in the play.