Refers to everything or all matters, often used in set phrases like 万事休す (all is lost) or 万事順調 (everything is going well). Slightly formal/literary.
Everything is going well.
万事休すだ。
All is lost.
Since we've prepared everything, it should all go well.
According to the report from the site, everything is going smoothly.
Since he has a lot of experience, I decided to leave everything up to him.
She paid attention to every detail to make the event a success.