It means my eyes don't actually go from the first word of a sentence to the end or even remain inside a sentence border when I read. There is alot of research on reading and eye tracking that shows this to be true.
Eyes jump around extracting what multiple sentences means as quickly as possible. They ignore word borders as well, chunking common or repeated phrases as a single rapid thing, and it is more a parallel process than a linear one.
Also, if you look up speed reading techniques they will warn you not to sound out the words. Basically, you can bypass the way a word is pronounced, which is slow, and you can still understand. I don't actually speed read, but read voraciously when I was young. An audiobook is very painful for me unless the narrator is extremely good because it seems so slow even at 1.25 speed.
If I actually wanted to speak what I am processing when reading English in a flow state, I couldn't. Because it is too fast and probably not grammatical. In addition, it's highly visual and largely bypasses auditory.
I try not to do this when reading Korean and try to sound out every word, because I am so bad at Korean. I think it's important to hear every word in my head, in order, but this isn't natural to me. Also, sounding things out stops me from making a huge number of errors and or inadvisable skips because I am not ready to read that quickly in Korean...but my brain wants to do it, and is doing it to some degree, as I naturally want to rapidly pull out the meaning and ignore the sequence of sounds that many assume are a necessary basis of understanding (and are not).