This image shows a portion of the Networking Advanced variables on the Create Stack, Configure Variables page.
This is two of five.

On the left there are steps indicating the workflow:
1 Stack information
2 Configure variables, which is in bold font to indicate it is the current page.
3 Review

There are fields with sample text
-Name of App server/PRCS Subnet
-CIDR of App server/PRCS Subnet
-Name of Database Subnet
-CIDR of Database Subnet
-Name of Fulltier Subnet
-CIDR of Fulltier Subnet