With Twitter Cards, you can attach rich photos, videos and media experience to Tweets that drive traffic to your website. We have added a few lines of HTML to your webpages so that users who Tweet links to your content will now have a “Card” added to the Tweet that's visible to all of their followers. Twitter Cards let you take your tweets beyond basic text adding visual interest through images, product info, videos, etc.
For Twitter Cards to work you must first add your Twitter handle to Marketing > You on the web section of your backoffice. You can validate out your URLs here: Read more