What does a blessing achieve?

[friend_mole]

What does it mean to bless something or someone, and who can do it?
A priest blesses people, and he blesses things – sacramentals, or objects like a house. What does that change in the blessed object.
Sometimes in church the people are asked to join in blessing, for instance, a couple celebrating their 50th wedding anniversary. Does this blessing actually accomplish anything?

 

[mosher]

A blessing is to help bring all things into the kingdom of God. When we bless things we take them aside and direct them to the use of the glory of God in a particular way. A Bishop, Priest or Deacon can do such blessings and are called sacramental blessings. However, for persons it is different. When we bless persons it has the purpose of helping to bring strength to that person so that they can live their life in accord with the Will of God ever more fully. When we as lay persons extend a blessing over a person it is to focus our prayer for the person. When a Bishop, Deacon or Priest blesses a person, using the sign of the cross, it imparts the power of God on the person to help make then holy.