Question

Difference between modifiability and expandability? explain.

Answer 1

You open a small fast food center, with a serving capacity of 5-10 people at a time. But you have enough space on hold to increase the serving capacity to 50 - 70 as your business gains traction. That's scalability.

You also have planned in advance to introduce more food items in menu, eventually converting fast food center to a full fledged restaurant. You plan to keep adding dishes when needed. That's extensibility.

To scale = to add capacity.
To extend = to add feature.