Baptism
Holy Baptism, a public rite of initiation, is the Sacrament by which God adopts us as God’s children. (Book of Common Prayer, 1979, 858). Through Baptism, God makes us members of Christ’s Body, the Church, and inheritors of the kingdom of God.
In baptism, we affirm that we belong to the God who is made known to us in Jesus, and we promise (or, if we infants or very young children, promises are made on our behalf) to live our lives in accordance with this deepest truth about who we are and whose we are
Baptisms occur during regularly-scheduled celebrations of the Eucharist, at which time all who gather agree to uphold the newly baptized in their life in Christ. Following ancient traditions, Baptisms may occur at the Great Vigil of Easter, Pentecost, All Saints’ Day, and the Feast of the Baptism of our Lord (Book of Common Prayer, 1979, 312).
Confirmation and Reception
“Confirmation is the rite in which we express a mature commitment to Christ, and receive strength from the Holy Spirit through prayer and the laying on of hands by a bishop.” (Book of Common Prayer 1979, 860).
Whereas full membership is conferred in the initiatory rite of Holy Baptism, Confirmation is a commissioning and empowerment for ministry.
Those baptized at an early age are expected, after a period of instruction, to make a “mature public affirmation of their faith and commitment to the responsibilities of their Baptism and to receive the laying on of hands by the Bishop.” (Book of Common Prayer 1979, 412).
Those who have been baptized in other denominations who have made a “mature public affirmation” will be “received” into the Episcopal Church through the laying on of hands by the Bishop.
It is a way of honoring anyone who has made a mature confession of faith in any other denomination by saying, in effect, we recognize and honor your spiritual journey in another fellowship, and we welcome you into the fellowship of the Episcopal Church, as you continue that journey. At Confirmation, an individual receives the laying on of hands by the bishop, thereby affirming their own faith and visibly connecting to the broader Body of Christ.
Reaffirmation
Reaffirmation is for people who have already been confirmed in the Episcopal Church. Some people presented to the bishop during the service of Confirmation are there to “reaffirm” their Christian vows. These might be people who have been away from the church for a period of time and want to make a new beginning. Others might be people who sense that they are at a new stage in their spiritual life and want to affirm this in ritual. Periodically, a spouse, fiancé or parent who is already a confirmed Episcopalian will go through reaffirmation as a way of honoring his or her family member’s decision to become a confirmed Episcopalian, saying in effect, “We are in this together.” We all go through many changes in our life’s journey, and reaffirmation provides a rite for those who want to take stock of their religious and spiritual life anew.
What is the difference between Confirmation, Reaffirmation, and Reception?
Confirmation is "a mature and public affirmation of faith and commitment to the responsibilities of Baptism" (BCP).
Reaffirmation means that you choose to re-state your commitment to Christ in The Episcopal Church, honoring your growth in faith throughout your spiritual journey. For many people, their path has wandered in and out of various denominations. Reaffirmation is a way to honor their journey and their previous public commitment as an adult while also making this definitive sacramental gesture.
Reception is common for people who have been active throughout their lives in other denominations.
Often, individuals who made a public profession of faith in a faith tradition such as the Baptist Church will choose to be Received into The Episcopal Church.
"I was baptized as an infant in another denomination, and then my family stopped attending Church. I only began attending again as an adult with my family. I want to join The Episcopal Church, but I don’t know if I need to be confirmed, reaffirmed, or received."
I would suggest that you be confirmed, because you have not made a mature affirmation of the faith. Your Baptism, once registered in the parish office, makes you a full member of The Episcopal Church. In terms of the sacraments, Confirmation is a way for you to reaffirm your faith and remain deeply connected to the Baptism of your childhood.
What is "apostolic succession"?
Apostolic succession is the teaching that those who have been consecrated (ordained) as bishops represent a direct, uninterrupted line of continuity from the Apostles of Jesus Christ. This teaching confers upon such bishops the authority to confirm church members, ordain clergy (including those newly elected as bishops), and exercise authority in their dioceses. So, those who have already been confirmed in a tradition that consecrates bishops in apostolic succession, do not need to be confirmed again in the Episcopal Church; they are said to be "received."