#1. A hashtag is any word or phrase preceded by the # sign that allows people to search for tweets about a specific topic.
#2. The document lists many commonly used hashtags related to education, including #edchat for general education discussions, #teaching for job seeking, and #edtech for discussions about educational technology.
#3. The hashtags are organized by topic such as technology, subjects, specific roles, and other educational areas. Popular subject specific hashtags include #mathchat, #HistoryTeacher and #scichat.