Most self-identifying Apostolic Christians aren't affiliated with an organization as I mentioned above. Of course, movements such as the United Pentecostal Church, has significant membership, and therefore is often relied upon by theologians to judge we Apostolics.
We call ourselves Apostolic because we adhere to, teach, and therefore live the Apostles' doctrine as outlined in the New Testament. We believe is Acts 2:38 is the Plan of Salvation, and that a life of holiness is commanded by scripture, without which none of shall see the Lord.