THE PROCESS EXPLAINED
One way to understand the Christian initiation process is by first breaking it down in to its three distinct aspects and by explaining the four periods into which the initiation process is divided. 

The three distinct aspects of the initiation process are: liturgical, catechetical and pastoral.  All three are equally important and are summarized below.

Liturgical formation – The RCIA process aims to lead participants to become “liturgical people”, (proclaiming the word of God through our practice of worship and celebration of the Mass) moving them towards full and active participation in the worshipping community.  Liturgy dynamically moves the process along by serving as “gateways”, of which there are three, into the major periods of the process (which are explained after this discussion).
Catechetical formation – This is the aspect of the initiation process during which the believer is formed in his faith and is instructed in the truth of the faith so that the believer may understand, confess and live that faith as a disciple of Christ, having been initiated into the fullness of Christian life through encountering God in worship, with Christ the teacher and the communion of other believers.
Pastoral formation – The pastoral components of RCIA are the people who participate in Jesus work of conversion and discipleship.  The pastoral work of the catechumenal process is accomplished through the love and labor of many people.  This pastoral work is a people-to-person endeavor.  By instruction and by the experience of authentic fellowship, the catechumens and candidates learn who God is, what his plan is and how to follow him as a member of the Christian community.

The Christian initiation process is divided into four periods:

1. The period of evangelization and the precatechumenate, up to the Rites of Acceptance and Welcoming (the first of the three gateways)
2. The period of the catechumenate, up to the Rites of Election and the Call to Continuing Conversion (the second gateway, normally celebrated on the First Sunday of Lent)
3. The period of purification and enlightenment (which normally coincides with the Lenten season)
4. Mystagogy; the third gateway, which occurs at the Easter Vigil.  This period traditionally spans the seven weeks of the Easter season, followed by the neophyte year, which lasts until the first anniversary of the initiation.

The process consists of three major rites or gateways that initiate the catechumen and the candidate into the faith.

1. The first is the Rite of Acceptance and the Rite of Welcoming, that establish and deepen the relationship between the Church and the participant and formally commences the participant’s preparation.
2. The next gateway, the Rite of Election for catechumens and the Rite of the Call to Continuing Conversion for candidates, begins the intense period of preparation for the sacraments of initiation. 
3. The third gateway is the reception of the sacraments of initiation, through which participants fully enter into the mystery of Christ.  This is the climax of the catechumenal process.