Today is the first day of Easter Triduum, the three days that lead us to Easter.
On Maundy Thursday we celebrate the Last Supper, when Christ instituted the Eucharist and the priesthood. Mass is celebrated for the last time until Easter Vigil, after which the altar is stripped and the Tabernacle is emptied. The Blessed Sacrament is carried away and often there is a Holy Hour in a "garden" so that we can pray as Christ asked Peter, James and John to do in the Garden of Gethsemane.
The following words are from the Eucharistic Prayer:
On the night he was betrayed, he took bread and gave you thanks and praise. He broke the bread, gave it to his disciples, and said:
Take this, all of you, and eat it: this is my body which will be given up for you.
When supper was ended, he took the cup. Again he gave you thanks and praise, gave the cup to his disciples, and said:
Take this, all of you, and drink from it: this is the cup of my blood, the blood of the new and everlasting covenant. It will be shed for you and for all so that sins may be forgiven. Do this in memory of me.