"Seated at the right hand of the Father" and pouring out the Holy Spirit on his Body which is the Church, Christ now acts through the sacraments he instituted to communicate his grace. The sacraments are perceptible signs (words and actions) accessible to our human nature. By the action of Christ and the power of the Holy Spirit they make present efficaciously the grace that they signify." (Catechism of the Catholic Church, article 1084)
We often think of Sacraments as the list of Seven Sacraments that you see listed to the right on the navigation menu. But, more fundamentally, Sacraments are "outward signs" of God's grace. These signs appeal to our senses (i.e they are not just deep thoughts in our heads or feelings in our hearts). Simply put, they are encounters with the real presence of God for the purposes of our salvation.
With that in mind, the First Sacrament--the concrete "outward sign" of God's real presence in human history--is the Mystery of the Incarnation: Jesus Christ. Jesus Christ is the sacrament of God, for it it through Him that we first come to experience the fullness of God's presence in our lives. The Church then, is the sacrament of Christ, for it is through the church that the world experiences the presence of God (i.e. the Body of Christ) in the world today.
The seven sacraments of the Church are invititations to experience the real presence of God in our lives but also a call for us to be outward signs that help make Christ more visible and a real presence to others in the world today. The Sacraments of Initiation welcome us so that we can welcome others. The Sacraments of Healing strengthen us and bid us to be forgiving and consoling of others. The Sacraments of Commitment commission us to share in the work of the Kingdom and the call of all the baptized to a life of holiness.