What is the difference between "presentation" and "demonstration"?

In the context of my work at a software company, a presentation would include powerpoint slides with lists or screen shots of software functionality. A demonstration would include using the software to show, or demonstrate the functionality or how to complete a task.

For one thing, a demonstration could involve hundreds of thousands of people marching through the streets, some of them maybe throwing petrol bombs.

A presentation rarely involves more than a handful of 'presenters', and usually it's just one person standing up in front of an audience and talking.

Without more context it's hard to be more specific. In some cases the words are interchangeable.