Basic terms, integration and usage of Twitter Cards
Twitter Card is a type of protocol which serves as a means of sharing information (image, text, and video) and promotion via tweets in order to enhance traffic towards a website.
The information shared via Twitter Card and tweets refer to Twitter only.
By simply adding a few lines of code to the web page’s HTML (exactly the same as in Open Graph Protocol) enables the users who share the link of the web page to get the Card in the link, along with basic data from the web page shared, so it becomes visible to their friends in the form of a snippet.
This way, you improve the promotion of web pages, information display quality, and enable better user experience while using Twitter.