… Benediction is the ritual for returning the exposed Blessed Sacrament to the Tabernacle. Before reposing it, a priest or deacon can give the blessing with the Blessed Sacrament. Acolytes (and EMHC) are also authorized to officiate at Exposition and Reposition, but cannot give the Benedection blessing.
Sometimes the whole ceremony is referring to as Benediction. But more specifically it is the actual blessing, the monstrance with the consecrated host is moved to make the sign of the cross. This is done by the deacon, priest or bishop.
The term “benediction” comes from the Latin word “benedictionis” meaning blessing.
In the liturgical book the heading “Benediction” is used as the heading for a longer period. It has:
“BENEDICTION
97. Toward the end of the exposition the priest or deacon goes to the altar, genuflects, and kneels. Then a hymn or other eucharistic song is sung. Meanwhile the minister, while kneeling, incenses the sacrament …
98. Afterward the minister rises and sings or says:
Let us pray. …
99. After the prayer the priest or deacon puts on the humeral veil, genuflects, and takes the monstrance … He makes the sign of the cross over the people with the monstrance … in silence.
REPOSITION
100. After the blessing the priest or deacon who have the blessing, or another priest or deacon, replaces the blessed sacrament in the tabernacle and genuflects. …”.
(From Holy Communion and the Worship of the Eucharist Outside of Mass, published by E.J. Dwyer, Sydney, 1975, ISBN 0-85574-401-4, pages 70-72).
It has a separate heading for reposition.