So begins Fox in Socks, by Dr Seuss (Theodore Seuss Geisel), a series of increasingly intricate tongue-twisters. Along the way, whether Seuss intended it to or not, it illustrates many points of English pronunciation and spelling.
Each of the words has four phonemes (distinct sounds) in pronunciation, represented by three, four or five letters in spelling, so immediately there is not a direct correspondence between sound and spelling. Each of the words starts with one consonant phoneme /f/, /s/, /b/ and /n/. The first three are represented by one letter, but the last is represented by two letters kn – the k is silent. It used to be pronounced but now it isn’t (long story). (In fact, the k is silent in all English words starting with kn.)