This is an example of bokeh – this is defined as the aesthetic quality of the out of focus regions of the picture and come from the Japanese word for blur. Enthusiasts believe there is good bokeh and bad bokeh, and also they judge a lens by its performance when out of focus.
I’m not a connoisseur so I don’t know how good my bokeh is on this occasion, but I have sympathy with the idea that focus can be overrated. Here’s the in focus version with the bokeh version layered over the top.
Canon EOS1 Ilford HP5+ 400