"As part of the new design, you can quickly view attachments—like photos—without opening or scrolling through the conversation. It’s also easier to switch between personal and work accounts, so you can access all of your emails without breaking a sweat. And just like on the web, you’ll get big, red warnings to alert you when something looks phish-y," Ray writes.
A big part of that is Google's Material Design language. That's really a fancy way of saying Google is updating the UI on its services to look modern. Beyond the aesthetic appeal, however, there is also an effort to make using Google's products easier and more intuitive.
"Gmail is a challenging product to design because there are so many users—1.4 billion—and such a breadth of ways that people use it," Gmail’s lead designer, Jeroen Jillissen, stated in a separate blog post. "It’s a productivity tool, and you never want to break people’s workflow."
The goal with the redesign, both on the web and on mobile devices, is to keep the focus on content. According to Google, the Material Theme helps "support user attention and productivity, as people tailor their email experience through density, labels, and inbox organization."