When people think about ranking social networks, it’s usually Facebook #1 and Twitter #2. Well, there’s a new #2 in town and that’s Instagram, who with 300 million monthly active users recently supplanted Twitter’s 284 million users.

Twitter was a compelling solution to a problem few understood. I’m not a big Twitter user by any means, but I’ve kept close tabs on it ever since its debut on SXSW, and my own understanding of Twitter has evolved a lot over the years.

Like most, I didn’t get Twitter the first time. It felt like a feature Facebook already had in status updates. Moreover, did I really want to know that people were doing on a real-time basis? Having lunch or going to the gym or feeling sad?

I soon realized it was a precise way of getting updates of only the people you’re interested in, which was/is different to Facebook’s algorithmic approach of getting updates from all your friends — who you may not actually be interested in following on a real-time basis. That was my first take on Twitter’s purpose.

As it turns out, few have the desire to publicly broadcast on a real-time basis what they’re doing. Only a small percentage produce the vast majority of Twitter’s content. So if that’s all Twitter is good for, Twitter would’ve been niche. An efficient distribution tool for people who like to talk about themselves and are interesting enough to get others to care. Not small, but not all that disruptive.

Twitter is more than that. Talking to my younger relatives about how they used Twitter back in 2009 opened my eyes. All their tweets were private and they used Twitter like an asymmetric group chat. Asymmetric because it’s opt-in (versus in chat apps, where everything posted to a group is seen by all its members). They used Twitter to semi-privately talk to their friends throughout the day.

Fast forward to 2014 and those formerly hardcore users have abandoned Twitter. Instead, they use chat apps like Whatsapp and LINE for private conversation, and prefer Instagram for asymmetric conversation. I’ll come back to the latter later on.

The third stage of Twitter is probably how most use it: interest-based news, updates and opinions. Like a town hall for what you’re interested in.

The town hall metaphor is quite accurate. Anyone can talk, but there are only a handful of people on the podium with access to the microphone; these are the giants with all of the followers. The rest of us are the crowd.

Only giants talk to one another — what insiders affectionately call the twittersphere — while we merely listen in on and nod with approval or hiss in disapproval.

Even here, Twitter has missed opportunities. If Twitter is a town hall, for newcomers, it’s hard to find the hall you’re actually interested in. Twitter has long tried to solve this onboarding issue, but the problem is fundamental: on Twitter, people are the unit of content.

I care about what Marc Andreessen has to say about technology and business; I don’t care at all what he thinks about the Hunger Games. Yet I can’t expect to get only one kind of content from Marc and not anything else when what I’ve committed to is following him and not the actual interest.

Experienced Twitter users understand this, and so have evolved their tweeting habits to reflect what kind of a brand they want to be on the service. Marc, for example, doesn’t talk about movies on Twitter. Unfortunately, it’s not easy for a newcomer to deduce who posts only relevant content and who does not.

If Twitter started from scratch, I wondered if instead of people, Twitter would’ve focused on interests as the fundamental unit of content? Onboarding would be about following your interests, and the service would be about helping you find the best opinions for that interest.

But now I’m describing Reddit, and I’m not sure if Twitter should be that either.

I suppose Twitter is the overlap between people and interests; where you want to follow the most influential in your interest groups to hear what they have to say.

That’s my current understanding of Twitter. Twitter is not for conversation, not for socializing and not for research. It’s for getting updates about what you’re interested in by following the giants of those interests, and then listening to those giants talk to one another.

This brings us back to Instagram. Twitter and Instagram are direct competitors, but despite the similarities, that Instagram is now used by more people than Twitter seems like an inevitability.

We tackle the why tomorrow.