Difference between ipp, ipps, http, https CUPS protocols?

[Kent West <westk@acu.edu>]

Probably answered somewhere, but I've been DuckDuckGo-ing for the past 
two hours and can't find the answer.

When adding a printer via the CUPS web interface (localhost:631) on my 
Debian box, Administration / Add Printer / Other Network Printers, there 
are four Internet Printing Protocol options:

https

ipp

http

ipps

Which one do I want to select? What are the differences?

Thanks!

--

Kent