Agape is the Greek word for God's love. God loves us unconditionally. If you are a mother, think of it as the type of love you have for your child. You'd do anything for that kid. Walk through fire for him. Jump out of a moving car for her. Get up at 4am for him. There's nothing you won't do for her.
That's Agape love.
In Book 2 of The Sisters of Gamma Omicron Delta Series, Courtney demonstrates Agape love, and Jim learns about it from her.