What does the term 'effectual call' mean in Reformed theology?

In Reformed theology, the 'effectual call' is a critical concept that denotes God's sovereign action in the process of salvation. It refers to the divine calling that effectively brings individuals to faith in Christ, ensuring that those whom God has chosen will respond positively to the gospel. Romans 8:30 illustrates this process, stating that those whom God predestined, He also called, justified, and glorified. This understanding emphasizes God's sovereignty and grace in salvation, recognizing that the call is not based on human merit but solely on God's purpose and will.