in short, what is democratic centralism & is it needed?

i have a fairly vague idea what it is, but I'd like a Leninist to explain what the principles of Democratic Centralism are and why its needed.

Democratic centralism is a compromise between divergence in opinion and unity in action. What it entails is the opportunity for all to state their case, to object to actions of the party, of government, or of whatever group they form a part of, but a complementary commitment to respect the decision of the majority and to carry it out, no matter one's personal viewpoint on the matter.

Why it's necessary: it allows for a balance between the dominance of the central authority (and the associated efficiency and coherency that stems from this) whilst allowing for a rich mixture of divergent opinions within the party structure itself. It is in many ways an active attempt to form a party structure in terms of Hegel's concept of a differentiated unity.