Thank you for the video. It was a bit of "fast talking" especially the GR bit, so it wasn't so satisfactory for me. The bit about acceleration causing time-dilation, for example
When she said that she had tried to read up about "Einstein" and not understood anything I was immediately reminded of this thread!
I think she tried to get to the basics that make up special relativity - without the maths - although there is, for me, unsatisfactory comments where she just says "these maths work". Actually, it does makes sense if you know where the maths comes from....sort of!
(Applying maths to the real world is always a bit head scratching.)