The buttons strung along above your emails used to have rounded buttons for deleting, archiving, and reporting spam. More importantly, you could label the emails. However, they added a nice feature where you simply just “move” the emails to a label called “move to” which definitely saves the extra step of having to archive the email. In the past you had to label then click on archive. Also, the buttons and drop down menus from them are now square it appears.
If you’re more curious about the nitty gritty details of the changes, click on this to go to the gmail blog.