The Typika is a service that can be conducted when a priest or bishop is not present. In some jurisdictions, it is a service led by a deacon, although forms of the service can be led by laymen. When held in a church the doors of the iconostasis remains closed and the service is conducted in the nave.
This Typika service is a form of Pre-Sanctified Liturgy held by a deacon authorised by the local bishop, when a priest is unavailable. The deacon distributes communion to the faithful present at the service. It should be noted that while this service is blessed in some jurisdictions, it is not universally accepted, nor is it of ancient origin. However, the idea of deacons bringing communion to those unable to attend the liturgy is an ancient custom, and so it can be argued that this ancient custom provides the basis for this more recent practice.
Typika on Days When there is No Liturgy, or a Vesperal Liturgy
According to the Typikon, Typika is appointed on those days when either there is no liturgy at all, or there is only a Vesperal Liturgy. Typika follows the Ninth Hour, and contains the Typical Psalms that would otherwise have been done as part of the 3 Antiphons of the Liturgy of the Catechumens. The text for this type of service can usually be found in the various Liturgicons and Horologions.
This Typika service is a specific form of service which mirrors the Divine Liturgy. It is used when a priest is not available or when a worshipper cannot get to a church. It is led by a deacon, subdeacon, reader, chanter, or the eldest experienced layperson present, in that order, unless a bishop or priest determines another leader.