Knot values decide the range on which a particular basis function influences.

In case of 'Uniform B Spline', knot values are uniformly spaced, non-repeating (single multiplicity) e.g. 0, 1, 2, 3, 4, 5, 6, 7

In case of 'Non Uniform B Spline', spacing changes (but they are always in increasing order) and there can be repetitions. e.g. 0 0 0 1 2 2 2. If 'k' is the order then first and last 'k' values are same (to pin it down to first and last points respectively) and middle values can be adjusted.