α-shape, is a family of piecewise linear simple curves in the Euclidean plane associated with the shape of a finite set of points.
— Wikipedia
Boum!. Let’s make it simpler. α-shape is a generalization of the convex hull concept. And the convex hull of a set of points is the minimal convex set containing all the points. Is typical to depict as some pins covered by a rubber band.
Representation of convex hull idea
α-shape me!
Castells 