Chances are if you're new to twitter, one of the most confusing aspects of reading tweets are the hashtags. (For the REALLY new, hashtags are words or groups of words immediately preceded by the # symbol, such as #marketing.)
I am going to break down for you what the basic types of hashtags are, and what they're used for.
It's common to see certain keywords hashtagged in tweets. For example, if someone is tweeting about marketing, they might include #marketing in the tweet.
Including a hashtagged keyword in a tweet makes it searchable in Twitter. Clicking on a hashatgged keyword (or searching by it in Twitter search functions) will pull up a list of other tweets with the same keyword. This allows your tweet to appear in search results for that keyword, making your tweet more visible. This is also a great way to find tweets, and tweeps, you're interested in via similar content interests.
2. Events and Conferences
Events can be anything from huge, multi-day conferences to a lunchtime or happy hour meetup where people are tweeting. Increasingly, events are promoting a specific hashtag for that event.
One the the functions of event hashtags is to help get the word out. Once the event starts, the event hashtag serves much the same function as a keyword, in that people wishing to follow conversations or information streams from an event can search by and follow the hashtag.
3. Twitter Q&As
Another type of 'event' is the Twitter Q&A. This is a Q&A session, typically around an hour long, done solely on Twitter. Everyone uses a specific hashtag to follow the session, and all questions and answers include it in their tweets.
Twitter Q&As are a fantastic way to learn more about a certain topic. The screenshot below is from #tchat, a weekly Twitter Q&A hosted by HR professionals. They talk about how to find jobs, network, build your resume, and a lot more.
Another great aspect of Q&As (not to get too far off topic) is that it's another great way to meet people on Twitter who have similar interests. This opportunity to expand your network is too valuable to ignore.
This kinds of hashtags are probably the most confusing to the new Twitter user. These are words or groups of words used to convey a part of the message, but which are not intended to be used to follow a conversation or to appear in keyword searches. They usually appear at the end of the tweet.
Some examples I've seen are #ilovecoffee, #AnotherDayInParadise, and #MondaySucks.
It's important to note, if you hadn't already noticed, that hashtagged terms can not have spaces or special characters in them. That includes hyphens and apostrophes.
That just about covers the major uses of Twitter that I can think of. Have you seen others? Any additional questions about how hashtags are used?