Pros:

• User-friendly interface and easy to set up

• Supports multi-factor authentication

• Auto-fills passwords on websites and apps
• Syncs across devices
• Smart device applications available
• Safari, Chrome, Firefox and Edge extensions are available

Cons:

• Can only be used with Apple devices
• No option to use offline

Summary: Keychain is best suited for users of the Apple ecosystem. It is preinstalled on any Apple device. Keychain is easily accessible on Mac and iOS devices and also supports multi-factor authentication. Keychain syncs across all Apple devices and allows for secure storage and sharing of various authentication credentials.

• secure password vault for storing user IDs and passwords (check iCloud data security overview)
• autofill (check Set up iCloud Keychain to autofill information on Mac and Automatically fill in strong passwords on iPhone)
• strong suggested password generator for creating passwords (check Create a strong password for a new account in iCloud)
• two-factor authentication (check AppleInsider: How to set up two-factor authentication in iCloud Keychain)
• biometric authentication (check Accessing Keychain Items with Face ID or Touch ID)

1. Open the Apple menu →  System Settings (or System Preferences). 
2. Click on your name, then select iCloud. In earlier versions of macOS, click on your Apple ID, then click iCloud in the sidebar.
   
3. Turn on Password & Keychain.
   

1. Open Settings, click on your name and choose iCloud.
   
2. Choose iCloud.
   
3. Tap Passwords and Keychain.
   
4. Turn on iCloud Keychain. You might be asked for your passcode or Apple ID password. 
   

1. Choose Apple menu→ System Settings. In macOS Monterey, choose Apple menu→ System Preferences. 
   
2. Click Passwords.
   
3. Sign in with Touch ID, or enter your user account password.
4. Select a website, then click the Show Details button . In macOS Monterey, click Edit.
   • To delete a password, click Delete Password.
   • To update a password, change it and then click Save.
     

1. Open Safari.
2. From the Safari menu, choose Settings (or Preferences), then click Passwords.
3. Sign in with Touch ID, or enter your user account password.
4. Select a website, then click Edit.
   1. To delete a password, click Delete Password.
   2. To update a password, change it and then click Save.
      

You can also use Siri to view your passwords by saying something like "Hey Siri, show my passwords."

1. Open Settings, then select Passwords. In iOS 13 or earlier, select Passwords & Accounts, then tap Website & App Passwords.
   
2. Use Face ID or Touch ID when prompted, or enter your passcode.
   
3. To see a password or passkey, select a website or app.
   1. To delete a saved password or passkey, tap Delete Password or Delete Passkey.
   2. To update a password or passkey, tap Edit.