The settings under notifications ought to have some tooltips that briefly explain what each notification type means.
For example, it's likely to be unclear what "Mention", "Page review" and "Edit revert" mean to a new users.
Version: unspecified
Severity: normal
There's currently a (tiny) "Learn more" link that points to detailed FAQ. I checked with Fabrice and I understand that tooltips for Echo preferences are already under being implemented and will be deployed shortly, probably within a week. I am closing this ticket as invalid, thanks for the report.