In a general sense, any Christian exercising a ministry is a minister. Since all the baptized are part of the universal priesthood whenever they engage in their vocation to evangelize the world and to help those in need, they are ministers.
In addition, the Church calls people to the responsible stewardship of their time and talent in support of the Church. This often takes the form of volunteering for a specific lay ministry, most of which are liturgical, catechetical, or involved in pastoral care and social justice.
Liturgical lay ministries include lectors (Ministers of the Word) who proclaim scriptural passages during the Mass, altar servers who assist the priest at the altar, music ministers who lead the singing, eucharistic ministers who distribute Holy Communion during Mass and/or who take Holy Communion to the sick and homebound, and ushers (Ministers of Hospitality) who welcome those coming into the church.
Other lay ministries include those who work with charitable activities, pastoral care and outreach, or advocacy for social justice.