Hashtags are important to the way we communicate online because social media platforms turn any word or group of words (without a space) that directly follow it into a searchable link.
The magic then happens when searching, as simply a #hashtag helps to populate groups of content; if you click on a hashtag you can see all the content associated with that group of words #hashtag in real time.
The purpose of the @mention symbol on social media is to ‘call out’ directly to someone. They will get notified that you have mentioned them. This is beneficial for businesses for a number of reasons, it lets the person or company know straight away, it puts you or your brand in front of who you are mentioning, it can leave a positive impression, and it encourages reciprocation.