What is the two-alphabetic caesar cipher?

Question

Encryption

I have a task:
Implement a two alphabetic Caesar cipher to encrypt and decrypt a string of any length and a given key, using the Latin alphabet and numbers, as well as only lower case.

Can you please tell me how this cipher differs from the usual Caesar cipher?

Answer 1

two alphabets are taken with different shifts and applied in turn, the first alphabet is applied to the first letter, the second to the second, the first to the third, and so on.

Answer 2

There is such a book, it is very easy to google (by the way, it also reads perfectly) - Simon Singh. Book of Ciphers.
There is a very detailed description of these ciphers.