There is going to be an update to the Google mail (GMail) interface. Not to worry, it is not a drastic redesign so you will be able to use it like you always have. It will look a little different and have some added functionality. As of now it is optional, so you can
continue to use the existing interface. If you would like to try using the new interface, there is an option for that. Eventually, Google will make the new interface standard for everyone.