Gmail has introduceda new promotions tab that turns emails into a grid of card-like blocks of content. Occasionally Gmail can automatically extract the content they need for this layout with no change to the original email.
However, many times they can't so they also provide a code structure
to give marketers control over this layout.
Click here for a diagram and example of the new layout »
Create Your Gmail Promotions Layout Code
Basic email-block overview:
Example of new layout: