Did you used MS Outlook or Windows Live Mail, then you must be aware of pane view feature, pane view allows you to look at the mail without opening it, you can delete it and take such other action without opening the mail.
Now you could get the same Pane View on your Gmail Account, it allows you to load mail fast and quickly reply to them.
Just like vertical and horizontal pane view in Outlook and Windows Live mail you could get it on your Gmail account.Google has added a new add-on to their Lab.
To get pane view do this :-
Log in to your Gmail account and then navigate to Labs, or just click HERE,
Now search for Preview Pane and then Enable it and Save it,
Now you will notice a new toolbar at the end of you mail toolbar in Inbox, click on it and choose the Pan view you want,