The command 'su' without a target user indicates that you want to:

When the command 'su' is executed without specifying a target user, it defaults to switching to the root user, which is the administrative account in a Linux environment. This command is a shorthand for "substitute user" or "switch user," and it is commonly used by system administrators to gain elevated privileges necessary for performing administrative tasks.

Using 'su' alone prompts the user to enter the root password, allowing them to access the root account temporarily. This action is essential for managing system-level configurations, installing software, managing users, and executing commands that require higher permissions.

Other options such as logging in as a regular or a system user do not apply here since specifying 'su' without parameters does not switch to those accounts. Additionally, 'su' does not change the working directory of the current user by default; it is primarily concerned with user identity rather than the current working directory context. Therefore, using 'su' directly leads to obtaining root privileges for the user, facilitating access to critical system functions.