Is that other people are on it. This best thing has three parts, three permissions to it:

It allows you to access the minds of inaccessible people. People have never been less accessible in the real world in my life. In normal times the barriers of time and distance remain. And yet others' ideas, interests, insights are right there on the screen. In between doing whatever is their priority in life they take time to share messages with everyone who cares to receive them. It's an embarrassment of riches of different perspectives that provides the weight behind the common twitter sentiment "can't believe this website is free."

It allows you to interact with these inaccessible people. This part feels almost too powerful at times. You can ask a question or reply to someone's tweet and they might reply back. And then you might reply back and you both leave the interaction having gained something. With individuals' attention valued higher and higher, being freely gifted any amount of an inaccessible person's attention is an awesome thing.

It allows you to tweak your brain through these inaccessible people. Lists let you run multiple experiments in parallel. Gather together happy people and read everything they write. Gather together artists and grow an appreciation for their unique styles. However you're curious about adjusting your thoughts, so many helpers are on twitter.