Publishing a thread one Tweet at a time lets followers feel the excitement of a developing story — perfect for a live event or an ongoing train of thought. Publishing an entire thread at once instantly gives your followers a fully-formed story — a better choice for a message you want to control a bit more, like a nuanced company announcement. If you want to curate your story further, you can organize your (and other's) published Tweets into a custom Twitter Moment.
Why Tweet in a thread?
Suspense! Intrigue! Drama?!
We've expanded our character count but it's still best to write your Tweets as concise, separate ideas that build on each other. (In the example above, I'd probably publish the first Tweet few hours before the 2nd to build excitement and the 3rd Tweet 15 minutes after the 2nd. So that it bumps back to the top of people's timelines.)
Below is an even better example of using a thread to create narrative and excitement.
@TwitterOpen — Twitter's resource group focused on supporting the LGBTQ community — Tweeted a thread to celebrate National Coming Out Day.
They used multiple Tweets to explain the significance of the day and launch the official hashtag. Each of the Tweets could stand on their own but, when threaded, they strengthen the message — which is ideal. This thread gains momentum and ends on a strong note (with an image) encouraging people to read the whole thing.