This is really cool material design card UI inspired accordion tab by Rafaela Lucas. There is an animation effect when you choose a tab, the tab title label gets a dropdown background and a text scroll effect and as the content is loaded the table label is also slid into the side of the content box.
If you are having trouble with the pen, try the archived copy on GitHub
Pretty Accordion Tabs Snippet
See the Pen Tabs – CSS + JS by Rafaela Lucas (@rafaelavlucas) on CodePen.default