App, Program, Software, Script, Process
Believe this is the most concise description I have seen.
- An app is complete set of functionality like a game
- A program is a piece of or whole of an app
- Programs are written with software
- Software is written with scripts or any one or more of various programming languages (please see my answer here: Jack Menendez's answer to In layman's terms, what are the major programming languages, and what are they used for?)
- A process is an isolated instance of a program running in a computer.
From: What is the difference between a program, an app, a software, a script, and a process? on Quora, question by Luca Dorigo, answer by Jack Menendez.