Interesting timing for this post - I'm studying this for a new job at the moment and building myself my own little Wikipedia in order to learn it. 10BASE uses Manchester Encoding, 100BASE uses Non-Return-to-Zero, Invert-on-one (NRZI) encoding and Multiple Level Transition (MLT-3) with 4B5B translation, 1000BASE uses 8b/10b Encoding (8 bits for data, 2 for ECC).

More recent speeds all tend to use PAM4 encoding, meaning there's 4 voltage levels instead of 2! There's a great article on it here: https://blog.samtec.com/post/understanding-nrz-and-pam4-sign...