At the time there were two branches, the win 3.1 branch, which was consumery, and the NT branch which was for servers / developers, etc. Cairo was an OS based on the NT branch, which was ultimately cancelled. Chicago was the project name for win95, which came off the 3.1 branch. Eventually the NT/3.1 branches merged, in the release called XP. And yeah, there's no such thing as windows 93.
Source: worked at msft from 92-97.