Imagine you have an account on Instagram and can follow a person on Twitter and comment her tweets without opening an extra account.
This #interoperability between services is possible in the fediverse with the Instagram and Twitter alternatives #Pixelfed and #Mastodon. It works on the basis of the #activitypub protocol.
For #influencers, #bloggers and also #companies this would mean: no need to maintain distinct online follower communities anymore. One just needs to choose, if one likes more the Instagram picture-based way or Twitter micropublishing way of online service.