There are many wonderful summaries on this site. Make the most of them.
But, to answer your question, here you go:
Macbeth is a play written by William Shakespeare. The play focuses on many different themes (including, but not limited to, ambition, fate, power, reality).
As for the action of the play, Macbeth, driven by a powerful prophecy that he will become king, takes fate into his own hands to insure the crown. Macbeth transforms from a loyal and noble man to a murderous madman.
Macbeth, led by his wife, decides to take control over the prophecy and murder so that he can gain the crown. After the murder, Macbeth struggles internally with the what he is done. Unfortunately, he fails to accept his downfall and becomes mad.
In the end, Macbeth is murdered (this fulfills the other aspect of the prophecy- Banquo's childen will inherit the crown).