What is 8/10 bit encoding?

Question

Electronics

In E. Tanenbaum's book, I read that in the PCI Express protocol stack, any device has the right to start a transfer at any time. But in this scenario, a problem can arise if the first few bytes are zero. This problem is solved by using 8/10-bit encoding. 1 byte is encoded as a 10-bit character. Question: how exactly?

Answer 1

https://en.wikipedia.org/wiki/8b/10b_encoding