An audience is a group of people who closely follow what you do and what you put out there. They actively engage with the content that you put out - be it blogs, articles, tweets, or videos - and usually also are subscribed to channels through which you share new content or updates.
An audience is not to be confused with a community.
An audience can be considered s ‘stepping-stone’ towards a community. The biggest incentive an audience has is a mutual interest towards someone or something, so that gives an edge towards converting an audience into a community.
Organizations who have users for a product are already on the cusp of fostering a community. A group of people already involved with a product would be highly likely to also be involved with a community of people who are using it too.