Corpus Christi is a Western Catholic feast. It is also celebrated in some Anglican and Lutheran churches. It honors the Eucharist, and as such it does not commemorate a particular event in Jesus' life. It is held on the Thursday after Trinity Sunday or, in some places, on the following Sunday. Its celebration on a Thursday is meant to associate it with institution by Jesus of the Eucharist during the Last Supper, commemorated on Maundy Thursday, and this is the first free Thursday after Paschaltide. In the current Ordinary form of the Roman rite of the Catholic Church, the feast is officially known as the Solemnity of the Most Holy Body and Blood of Christ.
In many English-speaking countries, Corpus Christi is transferred to the Sunday after Trinity Sunday by both Catholics and Anglicans. At the end of the Mass, it is customary to have a Procession of the Blessed Sacrament (often outdoors), followed by Benediction of the Blessed Sacrament. Corpus Christi is primarily celebrated by the Catholic Church, but it is also included in the calendar of a few Anglican churches, most notably the Church of England. The feast is also celebrated by some Anglo-Catholic parishes even in provinces of the Anglican Communion that do not officially include it in their calendars.
Corpus Christi is a public holiday in some traditionally Catholic countries including amongst others Austria, Brazil, Bolivia, Colombia, Croatia, Dominican Republic, East Timor, Liechtenstein, Panama, Poland, parts of Germany, Portugal, San Marino, parts of Spain and Switzerland, Grenada, Saint Lucia and Trinidad and Tobago. (From: Wikipedia, license: CCA-SA)