Wayne Grudem in his systematic theology book defines the term this way…
Effective (or effectual) calling is an act of God the Father, speaking through the human proclamation to the gospel, in which he summons people to himself in such a way that they respond in saving faith.This definition affirms the idea that God has an active role in the saving of people. If you have been a Christian for a while, you’ve likely wrestled with this concept. Is it God’s calling or man’s choice that leads one to saving faith? If you examine the scriptures, you must affirm that both are in some degree true. Having been raised under the teaching that man’s choice is the only influence in saving faith, as I grew in my faith and studied the bible I was shocked at how frequently the scripture affirms this idea of effectual calling. I felt a bit like I did after learning that Santa wasn’t real! How could the pastor I grew up listening to have promoted an idea that is so contrary to the truths that saturate the scriptures!?!?
In closing, I thought I’d leave you with a few of these scripture references that affirm the active role God takes in saving faith. Hopefully they will give you a greater appreciation for God’s role in our salvation and make you more courageous in sharing your faith, knowing that God chooses to actively work through your faithful witness!
Romans 8:30 - And those whom he predestined he also called, and those whom he called he also justified, and those whom he justified he also glorified.
1 Peter 2:9 - But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light.
1 Corinthians 1:9 - God is faithful, by whom you were called into the fellowship of his Son, Jesus Christ our Lord.
Acts 2:38-39 - Peter replied, "Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit. The promise is for you and your children and for all who are far off—for all whom the Lord our God will call."
Acts 13:48 - When the Gentiles heard this, they were glad and honored the word of the Lord; and all who were appointed for eternal life believed.