If people belonging to an offline community need to have space and time in common, something great about online communities is that the only things you need to have are a phone, wi-fi and interests you want to share.
While I see Facebook as a place where people rather to show off their problems or selfies instead of making worthy contacts, I watch at Twitter with a different light.
On Facebook you almost feel obligated to have your mum, your old high school friends or your ex as “friend”, on Twitter instead you feel free to follow whoever you want and whatever you want. Twitter gives the chance to create a different web of contacts made exclusively by your interests and people who share them. If you like a particularly band or TV show the use of hashtags can help you to find people who follow the same band or watch the same TV show.
I personally find it a really engaging social network that can help to find nice and new people to talk with and create new friendships based on common interests.