Notifications
Choose which emails you receive. In-app notifications in the bell are always on. Every email also carries a one-click unsubscribe link, and a busy thread sends at most one email per hour.
Discussions
Master switch for the three kinds below.
Someone replies in a thread you started, or to your comment.
Someone @mentions you in a thread or reply you can read.
Your reply is marked as the accepted answer.
Work
A task is assigned to you by name, or to a role you hold.
An unassigned task you could claim appears in one of your projects. Off by default: it fires for every task in every project you belong to.
A pipeline run you started fails. Runs you cancel stay silent.
A pipeline run you started finishes successfully. Off by default; the bell shows it either way.