When you send a SMS to TXTBOT, your message goes to the last person who texted the number. Between two people, it's simply an anonymous chat, but it gets more interesting when a few people are sending messages at the same time.
You can use this site to browse through people's interactions; each person is assigned a unique color so you can tell different senders apart. The feed is delayed by a few messages to maintain an air of mystery for when you inevitably want to participate. "Best" is a hand-picked collection of excellent conversations.