I didn’t understand it either but the pictures and graphs on this Wikipedia entry actually helped make a lot more sense of it to me, especially the analogy of the water faucet https://en.m.wikipedia.org/wiki/Heliosphere
That was a good page. At first I thought "But what is out there, outside the solar system?" under the assumption that there was nothing there. And there is nothing there, but nothing in galactic terms: the entire galaxy is there! And apparently it behaves like a gas, despite its low density.
So although solar wind sounds hardcore, at that distance its pressure about matches that of the nothingness that makes up most of the galaxy. Interesting!
