The Gospel as been described as a pool in which a toddler can wade and yet an elephant can swim. It is both simple enough to tell to a child and profound enough for the greatest minds to explore.Tim Keller, The Gospel in All Its Forms
I found this article to be so refreshing and helpful. I'll leave you with Keller's definition of the gospel (if it's possible to put the gospel into one statement, Keller does a fine job doing it):
Through the person and work of Jesus Christ, God fully accomplishes salvation for us, rescuing us from judgment for sin into fellowship with him, and then restores the creation in which we can enjoy our new life together with him forever.