How can I create an aliasing command for finding regular user names in my machine.

Have you done some research on the internet already?

The answer to your question is: "You can do that several ways.". I prefer to do it in a script, because I find filtering out non-privileged accounts easier that way, but it has been done as an alias before. I suggest a search at duckduckgo or google.

One thing to look for is a command that already exists to do that job. There is seldom a good reason to "reinvent the horse".

Local users are stored in /etc/passwd. This file consists of one line per user; each line has fields that are separated with a colon. The first field contains the user name, the third field is the user ID.

I am not quite sure what a "regular user" is. I would say any user except root. root has user ID 0.
So, get all lines that have a value different than zero in the third field, and print their first field. Personally, I would use awk for this. A combination of grep and cut should also cut it (pun intended).

The next question I have: What is an "aliasing command"? The shell has a command "alias" which allows creating a name for a string. For example:
creates an alias named lsf. Whenever you type lsf, the command ls -F is executed.

So I guess you have to create an alias in the following way: