Differences between apt-listchanges/unattended-upgrades/apticron/cron-apt

[<l0f4r0@tuta.io>]

Hello,

Can somebody explain to me the differences between apt-listchanges, unattended-upgrades, apticron and cron-apt please?

I have the following feeling:
* apt-listchanges: its main purpose is to indicate what's new between different packages versions. So it's handy to learn that new packages are available with an email alert (is it triggered automatically as soon as apt update finds something new?)

* unattended-upgrades: its main purpose is to upgrade your machine automatically. Personally, I use it to update my db & upgrade my vulnerable packages only (btw it triggers apt-listchanges)

Am I correct? Why would I need apticron & cron-apt then (I have Debian 9)?

Thanks in advance!
l0f4r0