Encryption
From Wikanual
Default internet pages are not encrpyted. The traffic between a web server and a web browser could be captured. In theory.
To avoid this possibility web browser and server can establish an encrypted connection. While normal connections start with http encrypted ones are indicated by https.
INTERDUBS lets you decide which connection to use per default. In general both http and https work.
While configuration variable for secure / encrypted connections can be set for your whole segment, specific client logins or looks, a segment wide setting will enforce the connection via https. Even if you enter the system via http or have disabled it in a look or login. The idea being that once security is on a certain level it should not be easy to be circumvented.