The collect (opening prayer) has four parts [not the parts I suspect you are thinking of - see * at the bottom of this post]. The collect I believe is a key to liturgy. Not as we so regularly experience it – a few seconds of just another little prayer near the start of a service, even read together from a printed pew-sheet for the day (reducing it to merely one part).
The word “collect” in Latin is collecta – gathering together. A collect gathers a litany (list of petitions) together into a final, single prayer. Or a collect gathers silent prayer together into a single prayer. This is what the collect is in the Entrance Rite – the Gathering of the Community. As it gathers the silent prayers of everyone it functions to gather the individuals into a praying community.
The bidding: The presider invites the community to prayer – “Let us pray”. Or in a more extended way, something like: “Let us pray in silence that God will make us one in mind and heart”.
The silence: This is the heart of the collect. This deep silent praying of the community is what the collect is collecting. No silent prayer and it is not a collect, there is nothing to collect. Without this silence the “collect” is reduced to merely another little prayer cluttering the vestibule at the start of our service.
The collect:* After sufficient silent prayer the presider proclaims the collect, gathering the prayers of the community, and articulating the prayer of the church – the body of Christ. As Christ’s body the collect is addressed in Christ’s name, on Christ’s behalf, to God the Source of all Being, in the power and unity of the Holy Spirit.
Amen: The community makes the collect its own by a strong “Amen” – “so be it”.
*The collect prayer itself can have up to five parts in its composition. There is more about that in the Gathering of the Community in Celebrating Eucharist. Some further history of the collect is included here.
The collect when well understood and aptly used can powerfully gather the community, deepen our prayerfulness, and profoundly express much at the heart of Christian spirituality.