The /etc/shadow file is a text file that stores encrypted passwords, along with user name, password expiration values, and last password change date. The credential information in the shadow file is encrypted using a one-way hash function to disable decryption. The /etc/shadow file contains one entry per line for each user listed in /etc/passwd file. Each line of the /etc/shadow file contains nine comma-separated fields, and the second field is the encrypted password of the user. The password field uses the $type$salt$hashed format, where $type is the method of cryptographic hash algorithm, salt is a random string, and hashed is the result of applying the hash function to the user's password and the salt. The /etc/shadow file is only readable by the root user, and it is used to enhance the security and control of user passwords.
The other information listed are not stored in /etc/shadow file, but in /etc/passwd file. The /etc/passwd file is a text file that contains basic information about each user account on the system. Each line of the /etc/passwd file contains seven colon-separated fields, and they are:
Username: The name of the user account.
Password: An x character indicates that the encrypted password is stored in /etc/shadow file.
User ID (UID): The numerical identifier of the user account.
Group ID (GID): The numerical identifier of the primary group of the user account.
User ID Info: The comment field that can store additional information about the user, such as full name, phone number, etc.
Home Directory: The absolute path to the user's home directory, where the user's personal files and settings are stored.
Shell: The absolute path to the user's default login shell, which is the program that runs when the user logs in to the system.
Reference:
Understanding the /etc/shadow File | Linuxize
Understanding /etc/shadow file format on Linux - nixCraft
/etc/shadow file format | Linux#
[/etc/passwd file format | Linux#]