Design
• New design for apps makes it easier to focus on your content and take action with space efficient toolbars and full height sidebars
• Updated menu bar features wider spacing and a new translucent material that becomes more vibrant when you interact with it
• Refreshed system sounds include the boot chime and sounds for transferring files, moving items to the trash, locking files, and more

Control Center
• Control Center puts your favorite menus and controls in one handy place in the menu bar so you can quickly adjust settings as you work
• Additional controls appear when you click to expand Control Center menus
• Support for pinning favorite menus from Control Center to the menu bar

Notification Center
• Updated Notification Center brings notifications and widgets together in one view
• Interactive notifications display additional actions you can take with a deep press
• Beautiful, new data-rich widgets for Calendar, Clock, Notes, Photos, Podcasts, Reminders, Screen Time, Stocks, and Weather
• Edit view lets you to add new widgets and customize their size
• Support for widgets from third-party apps

Safari
• World's fastest desktop browser with industry-leading performance and energy efficiency
• Customizable new start page lets you set a background image and decide what appears, including Reading List, iCloud Tabs, Privacy Report and more
• Expanded extensions support and new dedicated category in the App Store for discovering new extensions
• New tab design featuring favicons in tabs, and website previews that appear when you hover over a tab
• Translation (beta) for English, Spanish, Simplified Chinese, French, German, Russian or Brazilian Portuguese
• Privacy Report gives you visibility into how Safari keeps your browsing your business, with an overview of trackers blocked by Intelligent Tracking Prevention
• Safari password monitoring securely screens saved passwords for any that may have been involved in a data breach
• Safari privacy prompts for extensions let you choose when a website can work with an extension

Messages
• Pinned conversations keep up to nine of your favorite threads at the top of the list
• Mentions let you direct a message to an individual in a group conversation
• Inline replies let you reply to a specific message earlier in the conversation
• Message effects for balloons, confetti, lasers and more
• #images helps you find and add trending GIFs to messages
• Memoji makes it simple to create a personalized character and send stickers that match your mood and personality

Maps
• Guides offer recommendations for places to go and things to do, curated by a selection of trusted brands
• Look Around to explore cities in a high-resolution, interactive 3D experience
• Indoor maps for major airports and shopping centers
• Cycling directions helps you find bike-friendly routes to your destination
• Electric vehicle routing helps you plan trips for supported vehicles that you add on iPhone

List of supported models:
-MacBook (early 2015 or newer)
-MacBook Air (mid 2012 or newer)
-MacBook Pro (mid 2012 or newer)
-Mac mini (end 2012 or later)
-iMac (end of 2012 or newer)
-iMac Pro (2017)
-Mac Pro (end of 2013, mid-2010, mid-2012, graphics processor supporting Metal API is recommended)

Languages: English, Arabic, Catalan, Chinese (Hong Kong), Croatian, Czech, Danish, Dutch, Finnish,French, German, Greek, Hebrew, Hindi, Hungarian, Indonesian, Italian, Japanese, Korean, Malay,Norwegian, Polish, Portuguese, Romanian, Russian, Simplified Chinese, Slovak, Spanish,Swedish, Thai, Traditional Chinese, Turkish, Ukrainian, Vietnamese

Whats New

https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11_3-release-notes

HOMEPAGE

https://www.apple.com/