Solution
Elasticity is the ability of a cloud system to automatically scale resources (computing power, storage, or bandwidth) up or down based on current demand. For example, extra servers are added during a sale and scaled back afterward.
On-demand access means you can use computing resources whenever you need them, without a long setup process, like turning on a tap instead of digging a well. Extra storage for a school project can be rented and used at once.
Elasticity is automatic scaling with load. On-demand access is getting a resource immediately when you ask for it.