What are apps $($or "applications"$)?$

Small, downloadable software programs that can run on tablet devices or smartphones to provide special functions for these devices.

Small, downloadable software programs designed only for Apple products that provide special functionality for these devices.

Small, downloadable software programs designed only for Android products that provide special functionality for these devices.

Marketing software programs that measure the number of times a customer views a social media website ad$.$

Programs used to organize large groups $("$flash mobs"$)$ to form protests on social networking sites.