Make a demo that shows the process in action.

If you can't make a demo: people are better at understanding concrete vs. abstract. "Honda Civic" is better than "car" is better than "transportation device".

What that means in your case: describe the app by describing a concrete use case. Pick a concrete example instead of talking in abstract. Presumably you already have compelling examples of specific spreadsheets turned into web applications.

If you describe 2-3 concrete examples, they'll generalize themselves but it's much more difficult for people to start with generic explanation and imagine concrete examples.