Everyone who feels called to ministry inevitably asks the question - what does being "called" mean? After all, we understand that every Christian is called to live their lives in the service of and as a witness to Christ. So how is a call to ministry different?
Listening to the Puritans can help us understand the distinction of a call to ministry. The Puritans separate calling into two categories. The first is "general calling" which is the call on all Christians to live as followers of Christ. The substance of the general calling is essentially the same for all believers. The second is "particular calling" in which God calls people to different responsibilities within the church or within society-at-large. Thus, God particularly calls each Christian to live out the purposes of God through unique places of responsibility, tasks, or ministries, whether those are in the church, in vocations outside of the church, in their families, in relationships, etc.
So while others can feel called to the medical profession, engineering, education, motherhood, etc., when we feel called to ministry it means that we have begun to understand a particular calling God has made on our life to be in the context of a vocation as a minister in a church, as a missionary or in an organization or job that has ministry as its primary purpose and goal.