A hashtag is a word or phrase proceeded by a hash or pound sign (#) and used to identify messages on a specific topic. Think of it like like a label that makes tweets discoverable. When you click on a hashtag, you'll see other Tweets containing the same keyword or topic.
A Twitter handle is a username on Twitter, which you use in order to direct a tweet to a specific person, as in @bwestlibrarian.
To view someone's Twitter page, use http://twitter.com/ followed by their handle, as in http://twitter.com/bwestlibrarian.
Subscribing to a Twitter account is called “following.” To start following, click the Follow button next to the user name or on their profile page to see their Tweets as soon as they post something new. Anyone on Twitter can follow or unfollow anyone else at any time, with the exception of blocked accounts.
Your Home timeline displays a stream of Tweets from accounts you have chosen to follow on Twitter.
A response to another user's Tweet that begins with the @username of the person you're replying to is known as a reply. Reply by clicking the "reply" button next to the Tweet you'd like to respond to.
A Tweet that you forward to your followers is known as a Retweet. Often used to pass along news or other valuable discoveries on Twitter, Retweets always retain original attribution.
Some of these databases have scholarly articles (secondary sources), while others have news articles that can be used as primary sources or secondary sources, depending on what you are researching.
To find books, both primary sources and secondary sources, use these research databases.