What purpose does the secondary password serve? How can I change it?: The AMBIS secondary password is usually required for other services using IS AMBIS authentication. This password is used wherever you do not log in directly to the IS AMBIS IS (islogin.cz domain), e.g. access to IS AMBIS mail using POP/IMAP protocols, etc. A secondary password can be set directly in IS AMBIS if you know your primary password. You can do this in the same section where the primary password can also be changed.
The Information system Settings (gear icon in the bottom right corner of the page footer) Change secondary password

PozorPlease make sure that your secondary password is different from the primary one, as the former is sometimes transferred over networks in an unencrypted form, which makes it more vulnerable.