What do words ResNet, DenseNet, EfficientNet and SeResNext mean?

There was an item in my TODO list after Kaggle’s Bengali competition – to understand what these words mean as the winners were actively using these words :). I knew these are networks, but how they differ? I was going to read some overview paper about this and stop. In the problems which I’m solving now looking at the data (in particular, wrong predictions) is more important than choice between these networks, but anyway.
However, I had not find simple article with good explanation. There were some with copied pictures and quotes from the original papers. What the sense? It’s better to read the original papers with full content, isn’t? So I have read the original papers and drop here some notes about my understanding of them, may be it will be useful for someone.
I promise to be brief, don’t quote and don’t copy/paste.