I don't know which version of Faust that you are interested in: the two primary ones taught are either the poem by Goethe or the play by Christopher Marlowe. (The basic plot elements are the same).
Faust is a scholar who is never content with the amount of his knowledge The devil sees that the man is a challenge. Satan sends his minion, Mephistopheles, to offer Faust even more knowledge. To sweeten the deal, he promises him riches and pleasures beyond anything a scholar could have hoped for in mortal life. The trade for a life of ease and unlimited knowledge is Faust's soul.
Faust makes the deal, thinking that he can ultimately outwit the devil. He is wrong. Mephistopheles tells him:
In the end, you are exactly --what you are.
Put on a wig with a million curls,
put the highest heeled boots on your feet,
yet you remain in the end just what you are.
Or, from Marlowe's play Dr. Faustus:
Faustus: The stars move still, time runs, the clock will strike, the Devil will come, and Faustus must be damn'd. O, I'll leap up to my God! Who pulls me down?... O spare me, Lucifer!" (1.14).
The lesson in any version of the Faust tale is that there are things in heaven and earth that are not dreamed of in philosophy (to paraphrase Hamlet) and that no matter how much treasure you have on earth, you can't take it with you.