the meaning of the different ceremonies of the Mass

the Roman Catholic Mass is built around the Eucharist, modeled after the Last Supper and intended to renew that divine mystery.  Here is a statement on the Eucharist from article 47 of the Vatican Council Constitution on the Divine Liturgy :

"At the Last Supper, on the night he was betrayed, our savior instituted the Eucharistic sacrifice of his Body and Blood. This he did in order to perpetuate the sacrifice of the Cross throughout the ages until he should come again, and so to entrust to his beloved Spouse, the Church, a memorial of his death and resurrection: a sacrament of love, sign of unity, a bond of charity, a Paschal  banquet in which Christ is consumed, the mind is filled with grace, and a pledge of future glory is given to us."