Also known as the Most Holy Body and Blood of Christ, this feast honors Jesus Christ, Really, Truly and Substantially Present under the appearances of bread and wine. This Presence happens through the change which the Church calls transubstantiation (“change of substance”), when at the Consecration of the Mass, the priest says the words which Christ Himself pronounced over bread and wine, “This is My Body,” “This is the chalice of My Blood,” “Do this in remembrance of Me.”
In 2023, the Solemnity of Corpus Christi is on June 8, but it is transferred to Sunday, June 11 in some dioceses. (Source: https://www.ewtn.com/catholicism/seasons-and-feast-days/corpus-christi-14356)