My mental model of Span, Memory and ReadOnlySequence in .NET

Saying that I disagree with the documentation of the new memory abstractions in .NET would be an overstatement. After working a bit with Span, Memory, ReadOnlySequence and IBufferWriter I model it in my head in a bit different way. Each of these terms has a one line definition that one could reason from. I hope that newcomers to this memory friendly world will think of it a good primer. At the same time, I hope it delivers a refreshing view for more experienced engineers. It does not aim to deliver the whole description. It aims to be a useful model as all models are wrong but some of them are useful.