Because a chapel is smaller and more intimate than the church it may sit beside or within, it typically supports a different register of devotion than the main liturgy: personal prayer before a particular image, private confession, a memorial mass for the dead, or veneration of a relic kept nowhere else in the building.
A Lady chapel, dedicated to Mary and often positioned directly behind the high altar in English cathedrals, gave a distinct focus for Marian devotion separate from the cathedral's principal worship. Chantry chapels, endowed so that a priest would say masses in perpetuity for a specific patron's soul, turned side chapels into a form of long term spiritual investment, and their proliferation in the later medieval period reflects how central the concept of intercessory prayer for the dead had become before the Reformation curtailed the practice in Protestant regions. Institutional chapels, in hospitals, universities and military settings, carry a more practical devotional role, offering worship access to people who cannot easily reach a parish church, and many are deliberately designed or furnished to accommodate more than one faith tradition. Across all these settings, the chapel's smaller scale is not a lesser version of the church but a different instrument, built for individual or small group devotion rather than the full congregational assembly a parish church is designed to hold.