A formal, somewhat literary yojijukugo meaning 'all matters' or 'everything under the sun'. Often used in official or written contexts.
Everything is ready.
The company president keeps an eye on all matters.
万事 is a more common word for 'everything' or 'all things', while 諸事万端 is a formal yojijukugo with a similar meaning but a more literary feel.
諸事 means 'various matters' and is a component of 諸事万端. It is less emphatic than the full yojijukugo.
A yojijukugo composed of 諸事 (various matters) and 万端 (all aspects). The exact historical derivation is uncertain, but it is a conventional compound used to express comprehensiveness.