I am not computer savvy, I don't want you all to laugh at me. When I set up my cell phone I used the same email address that I use on my home computer. Needless to say, I get all my emails on my cell as I do my home computer. I don't like that. Can I set up a different email address for my cell phone, and if I do that will that delete my email address from computer?
Obviously not. It is even possible to add a variety of email accounts on your LG G3 including personal email and work email . But for your case, simply add a new adress. Create your secondary email adress and delete the main adress (from the phone: settings > account > Google > [your address ] > delete).
Now you have two addresses, one on the computer, the other on the phone.
I understand from your question that you do not want to receive any email from your "computer" email account, onto your phone.
For that you can remove your current account from your phone, and add a new one. Simply go to settings -> accounts -> Google -> "firstname.lastname@example.org". Now open the menu (three dots on the top right) and select "remove account".
This will remove the account from your phone, but you will still be able to access this account from your computer.
Now you can add a different account. Open settings -> accounts. And press in "add account" -> "Google" there you'll have an option to add an existing account, or to create a new one.