TCB

how tightly the curve bends at the point: 1 gives zero tangents, so the curve runs straight into and out of the point; negative values give rounder curves

how sharply the direction changes at the point: -1 gives a corner along the incoming and outgoing edges, 1 an inverted corner, 0 a smooth curve

the direction of the tangent at the point: 1 along the incoming edge, so that the curve overshoots after the point, -1 along the outgoing edge, so that it overshoots before it, 0 their average