A classis is a group of churches within a geographical area that comes together to seek, discern, and submit to God's will, offer one another mutual support and accountability, find ways to live out a collective calling in the region, and allow for a healthy and sustained connection to the wider denomination.
A classis has the authority to deal with matters that concern its churches in common and its decisions are binding on the churches in its region. A minister, elder, and deacon from each congregation are delegated to attend each classis meeting.
Our Church Order defines classis in this way: "A classis is a group of Christian Reformed churches that come together to seek, discern, and submit to God’s will; offer one another mutual support and accountability; find ways to live out a collective calling within their region; and allow for a healthy and sustained connection to the wider denomination. A classis shall consist of a group of neighboring churches. The organization of a new classis and the redistricting of classes require the approval of synod."
Read more about the purpose of a classis.