help me to understand the below highlighted:
When the login program executes a shell, that shell is uninitialized. When a shell is uninitialized, important
parameters required by the shell to function correctly are not defined.The shell undergoes a phase called initialization to set up these parameters. This is usually a two step
process that involves the shell reading the following files:
The process is as follows:
1. The shell checks to see whether the file /etc/profile exists.
2. If it exists, the shell reads it. Otherwise, this file is skipped. No error message is displayed.
3. The shell checks to see whether the file .profile exists in your home directory. Your home
directory is the directory that you start out in after you log in.
4. If it exists, the shell reads it; otherwise, the shell skips it. No error message is displayed.
As soon as both of these files have been read, the shell displays a prompt: