A user meta in WordPress is a set of distinct, different, and customized text fields for each user according to his or her preferences. In other words, WordPress user meta allows you to add whatever information you wish about your users. Update_user_meta() is the function you use to add or update a user's metadata. It looks as follows:

update_user_meta( $user_id, $meta_key, $meta_value, $prev_value );

Here,

• $user_id: User's ID to be affected.
• $meta_key: Name of user meta field to be altered.
• $meta_value: The value to be assigned to the user meta field. You may use integer, string, array, etc.
• $prev_value: Used for handling duplicate meta keys. Normally you can omit this option.