Hashtags were originated on twitter and it is a way by which users categorize their tweets following a particular theme. If a user wants to tweet about something like an event then he is likely to look at other tweets that have the hashtag related to that event. If you use a hashtag you can make yourself visible to a great number of relevant audience.
Top brands of the world have already started the practice of using hashtags and the results driven were phenomenal. Many business conferences are now seeing the use of hashtags where visitors are using it them as a medium to communicate to the speaker. They may just ask a question by using the relevant hashtag. Now just imagine what will be the potential reach if someone uses a hashtag related to your brand. It is just like the fire in the jungle where you just need to ignite one spark and the job is done.
To use a particular hashtag you must know exactly what the event is all about because by using the twitter account of your brand you actually represent the brand. If you are conceptualizing a new hashtag then proper research is required. There are some must dos for better performing hashtags like the hashtag must be small, easy to use and must generate a wave among the audience. To make things interesting you can even award someone using your hashtag that can further help boost your campaign. There is another advantage of using hashtags that though they help you increasing their reach yet they are free of cost.