The # symbol, or hashtag, marks keywords and topics in a Tweet (photos, videos, links and up to 140 characters of text). Created by Twitter users as a way to categorize messages, today it has proliferated in ways unimaginable and there is empirical data which suggests that everyone should be using hashtags today.

And while intended to address relevant topics and generate dialogue and community, there has been criticism of overuse in recent years.   One of the greatest lessons in social media etiquette was delivered in the memorable sketch between Jimmy Fallon and Justin Timberlake in 2013.