To highlight text on Medium, select it > click the highlighter icon.
Highlighted text will turn green, and your followers can see your highlights on post pages and your profile.
When many readers highlight the same line or paragraph of a post, you'll see a Top Highlight message in the sidebar.
You can also share highlighted text to a connected Twitter account by selecting it > click the Twitter icon. A text shot image of your highlighted passage will be automatically generated and added to your tweet.