When you blow a giant bubble, its surface stretches enormously. If the film can't keep up with that stretching by spreading it out evenly, a thin spot forms and the bubble pops. Elasticity is exactly that ability to stretch uniformly and "bounce back."
Where it comes from
It comes mainly from the polymer and its extensional viscosity: long chains resist letting the film thin out suddenly. The surfactant also adds a self-healing effect (the Marangoni effect). Together, they make a tough, resilient film.
Blending polymers (see polydispersity) boosts elasticity while using less product. At KUANTIKA, elasticity is one of the three physical metrics our engine calculates, alongside duration and strength.