Communal prayer begins with the chazan's exclaiming "Barechu et Adonai Hamevorach", "Bless God, the Blessed". Before that, the morning prayer opens with blessings and praises that may be said by an individual and do not need a minyan. The congregation's response is to answer "Blessed is God for ever and ever", while bowing.
Blessing God is a form of praise, as in "David blessed the Lord in front of the congregation" (I Chronicles 29:10) and is related to the word berech, knee in Hebrew. Kneeling is a form of praise.
Rabbi Akiva teaches that every dawn, a heavenly representative of Israel declares "Barechu et Adonai Hamevorach!" Our earthly Barechu is modelled after its celestial counterpart. Just as Barechu unites all the various angels in praise of God, so too, Barechu focuses both the chazan and the congregation on prayer. The medieval scholar Eliezer Ben Nathan sees Barechu as the chazan's seeking the consent of the community to pray on their behalf and their granting it in response.