Blessings - Benedictions

A Blessing or Benediction...

asks or pronounces good things
upon or for someone

it is well speaking
(bene [as in beneficial] = well + diction = speaking)

simple:
a prayer aloud or written out - done by anyone
for or over someone else (family, friends, etc.)
asking God's blessing to be upon them
asking His help and care for them
in general, and on special occasions
(marriage, births, when embarking on long trips, new jobs, etc.)

formal:
a pronouncement - usually by clergy
for or over the congregation
at the end of public worship, and on other occasions
invoking God's Name (asking God to put His Name) upon His people
asking His blessing on His people
(for grace, mercy, faith, unity, protection, comfort, etc.)

usual formula: 'May the Lord...' (do this for you)

~

(expanded)

sample of constructed blessings - benedictions using the Scriptures:

May grace and peace be multiplied to you in the knowledge of God and of Jesus our Lord. (2 Pt 1:2)

May the God of our salvation keep you steadfast, immovable, always abounding in the work of the Lord. (1 Cor 15:58)

May the Lord cause you to increase and abound in love for one another and for all people. (1 Ths 3:12a)

May the God of all grace, Who called you to His eternal glory in Christ, perfect, confirm, strengthen, and establish you. (1 Pt 5:10)

(the Aaronic blessing used by the priests in the OT - Num 6:24-26)
The LORD bless you, and keep you,
The LORD make His face to shine on you, and be gracious to you,
The LORD lift up His countenance on you, and give you peace.