A simple 3-question catechism adapted from Cameron Cole’s Rooted Ministry blog. 
- What does Gospel mean? Good news.
- What is the good news? God loves sinners through the life, death, and resurrection of Jesus Christ.
- Is the Gospel about what God has done for us or about what we do for God? About what God has done for us.
Volumes have been written about each of these questions but I think they effectively sum up the foundations of the Christian faith.