MakeUseOf: “What Private Browsing Does in Safari – First and foremost, Private Browsing keeps the website pages you visit out of your History. The aim is to prevent someone else from seeing which pages you have visited if they have access to your phone or computer. In Safari, Private Browsing does a lot more than just hide URLs. It also:

• Prevents recent searches from showing up in your history.
• Stops remembering details you enter in forms for autofill.
• Keeps downloaded items from appearing in your Downloads list.
• Locks private tabs after a period of inactivity.
• Adds tracking and fingerprinting protection.

However, it’s important to note that Private Browsing does not stop you from being tracked altogether. Websites you visit will still be able to use various methods to track you, and will still have access to all data that you send them. On macOS, iOS, and iPadOS, Safari groups private tabs together, and separates them from non-private tabs. On Mac, each Safari window is either private or non-private, and can have as many tabs as you want.”