As a sacrament, the Eucharist has a double aspect: it is
both a sign and the reality signified by it, both a remembering
of the past and a making-really-present: "When the Church
celebrates the Eucharist, she commemorates Christ's Passover,
and it is made present: the sacrifice Christ offered once
for all on the Cross remains ever present" (CCC 1564).
Here the three meanings of "present" come together:
Christ in the Eucharist is 1) present, not absent, but really
here; 2) present, not past, but happening now; and 3) presented
as a gift (a "present"), really given; offered,
Christ is "present in many ways to His Church"
(CCC 1373) but "[t]he mode of Christ's presence under
the Eucharistic species [forms, appearances] is unique. It
raises the Eucharist above all the sacraments as 'the perfection
of the spiritual life and the end to which all the sacraments
tend'201 [St. Thomas Aquinas]. In the most blessed sacrament
of the Eucharist 'the body and blood, together with the soul
and divinity, of our Lord Jesus Christ and, therefore, the
whole Christ is truly, really, and substantially contained.'
. . . [I]t is presence in the fullest sense . . . Christ,
God and man, makes Himself wholly and entirely present"