No, this isn't one of those annoying Get more followers campaigns to artificially inflate your following on Twitter with irrelevant followers. This is how to effectively increase your voice on Twitter so that your tweets are found by relevant audiences who aren't following you.
A hashtag is the pound sign # followed by a tag that explains what the topic is that you're writing about. If I'm writing about the economy, I might write #economy within my tweet. If I'm writing about Indianapolis, it might be #indy. If you're utilizing Twitter for business, effective use of hashtags is a must.
Ever wonder who used the first hashtag? You can thank Chris Messina in 2007 on Twitter!
how do you feel about using # (pound) for groups. As in #barcamp [msg]?
— Chris Messina™ (@chrismessina) August 23, 2007
Here's an example. When we released the WordPress Image Rotator, we could have simply tweeted that it was released and our followers would have read about it.
Instead, we added hashtags #wordpress and #plugin to the message:
— Marketing Technology (@martech_zone) September 2, 2014
The Tweet was immediately picked up and retweeted by several accounts monitoring those hashtags, leading to hundreds more installations of the plugin. Oh, and this is also a good way to pick up relevant followers! 🙂
Here's a great infographic from Leap on the history and usage of hashtags in social media.