All of C.S. Lewis's talk about mythological creatures can have you stumped, here you can read up on some of these mythological creatures, and link to other informational sites.

Centaurs go back to Greek mythology, and were said to be the born of Ixion, the son of the god Ares, and a cloud. They have the head, arms, and chest of a man, but their whole lower half is horse-like. In Greek history, centaurs were said to live in Thessaly and eat meat. They were usually described as being drunk.

In the story, Mr. Tumnus was a faun. This means that he had an upper body of a human, but the lower body of a goat. Fauns usually have two small, sharp horns on their heads and ears that are pointed like that of an elf. Fauns are very fond of music, and some play more than four or five instruments.

In the book, the White Witch's sledge driver is a dwarf. In the series dwarfs are mostly miners and goldsmiths. They also have red or black hair.

When Aslan hands himself over to the witch to be killed on the Stone Table, it mentions many different mythological characters like ogres, hags, incubuses, wraiths, horrors, efreets, sprites, orknies, wooses, and ettins.

In mythology an incubus is a male demon. This word in Latin means nightmare.
Sprites are disembodied fairies that can fly without wings. They are very shy and hate ugliness and evil in any form. Ettins are a rare race of giants, while Efreets are supernatural beings who usually are described as not being kind or friendly toward humans. A wraith, or ghost, is a spirit that appears to hint or warn of evil to come.

Some of the other beings mentioned, like orknies and wooses could have been made up by C.S. Lewis himself. Also, horrors could just symbolize evil itself.