Part of the viva process is your examiners exploring your significant, original contribution. They will want to discuss your work with you, to find out more about it, to see what it means, to see how it applies, maybe find the edges or exceptions. Whatever their questions though, it’s all about what you did.
And what you did was make a difference.
You’ve changed what was before and made something new.
There’s a time and a place for summaries and defining what you did. Start with appreciating first that you did it. You made a difference. Through your effort, your learning, you skill and your time. You made a difference. You did it. Something exists because of you. Remember that before you do anything else for your viva.
You made a difference.