The Gmail team has introduced a few changes to the buttons on Gmail.
To begin with, you will notice that the button styles have changed. They are sharper than before.
Apart from the style change, Gmail has introduced two new buttons, Move To and Labels .
The Move To button will help you to better use labels and this button also gets labels closer to folders. In a traditional set up, whenever you move a file to a folder, the file would be transferred out of its current position and moved to the folder. Exactly the same way, whenever you move a mail into a label, the new label would be applied to the mail and the mail would be Archived meaning it would not be in your inbox after that.
The Labels button is to only apply a label to the mail and not Archive it.
I guess the names speak pretty well. Move To meaning move the mail to this label and Labels meaning apply this label to the mail.
Thanks Gmail Blog