Macbeth's main desire in Shakespeare's Macbeth is for ambition. He wants to be king.
He is predicted to be king by the witches, but they predict no time-line for his being king. He doesn't want to wait and see, however, so he immediately thinks of the quickest way to the throne--assassination.
Being king, however, soon is not enough for Macbeth. Once he has the throne, he wants more--a dynasty. At the time he is predicted to be king and Banquo's heirs are predicted to be kings, Macbeth doesn't give Banquo's heirs a second thought. But once he has the throne, then he wants more. He wants his heirs to rule.
Macbeth's desire is for power, and whatever else comes with it.
Other desires are mentioned at different points in the play--he'd like to get away with what he does and to rule without worries, and he desires that life actually had some meaning in his famous "Tomorrow" speech--but his overwhelming desire is his ambition.
I assume that you are referring to this line from Act I, Scene 4:
If so, then what Macbeth desires is to have more power. In particular, he desires to become the king of Scotland.
What has happened here is that the witches have predicted that he will be the Thane of Cawdor and the king. Now, he has unexpectedly found out that he is the Thane of Cawdor. When he finds that out, he speaks the words I've quoted above. He is talking about his desire to become king.
He is showing that he knows that this desire is wrong.
MacBeth had a desire to exert an influence over his own future and take matters into his own hands. He also had a desire for knowledge - and in particular knowldege about the future and what it held for him. One of his character traits was impatience and he could not wait for events to take their own course. MacBeth also had a desire to keep certain things to himself - he does not tell his friend his true thoughts about the witches prophecies, but guards them secretly, fanning the flames of his own ambition and desires for control and status. To begin with, he desires what Lady macBeth wants too - but then their paths diverge and he goes on alone and out of control.
Macbeth desires that he become the King of Scotland. He initially is introduced to the reality of this possibility by the witches who tell him that he will become a king. When he shares this information with his wife, she wants him to do something to make this event happen much faster than waiting for the king to die.
With Lady Mcbeth's manipulated guidance, the two plot to kill the King. Macbeth carries out the murder and feels relatively safe. He knows that there is a way that he can lose his throne but misinterprets the witches’ words. His ambition and greed and the prophecy lead to his downfall.