As a platform, Twitter has, of course, evolved, and the way people interact with it has, too. One of the innovations that have come from experimentation is how to signal a “thread” of Tweets. Currently, when you see the “1/,” that signals that there are more Tweets to follow on this same topic. If you know in advance how many Tweets will be in the thread, you can give a concrete number, e.g., “1/10.”
After you’ve Tweeted your initial content, you want to reply to your own Tweet and a pop-up will prompt you to “Add another Tweet.” You can do this as many times as you need to tell your whole thread. If you know ahead of time that you’re going to be writing a long thread, you can also draft it ahead of time by clicking the plus icon to the left of the Tweet button and then publish it all at once by selecting Tweet all.
Your initial Tweet should also cue your followers to what is coming in the thread (this would be a good time to establish if you’re planning on telling a true story or not). For example, you could say, “I’m at the post office, and you won’t believe what’s going on here 1/.” It teases the story that’s coming, tells your followers it’s currently unfolding, and signals there are more Tweets to come.