A - Thanks for the question. A blessing is a prayer in which we invoke God's favor over a person(s) or object(s) for the purpose of setting them aside as being under God's care. It is not a magical chant that actually changes the nature of the object or person.
Blessings are considered Sacramentals. Every Sacramental is a sacred sign (an object or action) which bears a likeness to the Sacraments and whose effects are obtained by the prayer of the Church.
The Catechism says:
Sacramentals derive from the baptismal priesthood: every baptized person is called to be a "blessing," and to bless. Hence lay people may preside at certain blessings; the more a blessing concerns ecclesial and sacramental life, the more is its administration reserved to the ordained ministry (bishops, priests, or deacons). - CCC 1669So, depending on what or who is being baptized and for what purpose, the blessing may or may not be reserved to the ordained. For instance, those things which are more closely connected to a liturgical or ecclesial (thus related to the Church) reason are more likely to be reserved to priests, deacons, and/or bishops.
An example would be the blessing of a rosary, palm branches used on Palm Sunday, and the blessing of ashes for Ash Wed. Lay persons do not bless any of these things. Rather, the blessing is reserved to the clergy.
On the other hand, lay persons are free to bless their children, family, food, etc.
The blessing of a lay person is no different from the blessing of a consecrated religious.