What Apple say about macOS

Notification Center is now more iOS-like, with grouped notifications inline with widgets, and all interactive.

Safari: improved performance and energy consumption, new privacy protections, more customizable home screen, in-tab previews, data breach notifications, privacy reports, on-system translation service.

Messages: group tracking, contextual linking, pinned conversations, inline replies, mentions, group photos, improved Memoji, stickers, hashtags and message searching.

Maps: new trip-planning tools, location research tools, guides, EV and bicyle-centric route planning, 3D look Around, charging station tracking, indoor maps.

App Store: Safari Extensions get their own area, privacy information enhanced.

Photos: retouch now machine learning enhanced.

Peripherals: AirPods now automatically switch across devices using macOS 11, iOS 14, iPadOS 14 and later.

HomeKit: improved face recognition and activity zones.

Music: iTunes/Apple Music now includes a Listen Now tab for curated music.

Siri: better website integration.

Software Update: improved updating mechanism; non-interactive bits happen in the background, update process sped up.

Startup: The Mac startup chime is once again played by default upon booting.

USB: Added USB4 support.

Apple Silicon: Added support for new Macs with the Apple M1 processor, the MacBook Air, MacBook Pro and Mac mini.