Flexibly configure any sort of reminders and alarms based on the Joint Calendar special feature: https://apps.odoo.com/apps/modules/9.0/joint_calendar/. Alert at any moment of time regarding any event or action

They are both filters, domain is like a hard filter, context is like a soft filter.

Domain is used purely for filtering to control the records that are available in the tree/list and form views.

Context is used to pass filtered data to the server to functions.

You cannot remove context to expand the data beyond what domain allows you to see. But you can remove context to see everything domain allows you to see.

There is probably a more detailed and involved explanation, but this is what it boils down to.