WordPress.com
Taken directly from WordPress.com’s “About” page…
“At WordPress.com, our mission is to democratize publishing one website at a time.
Open source WordPress is the most popular online publishing platform, currently powering more than 26% of the web. We wanted to bring the WordPress experience to an even larger audience, so in 2005 we created WordPress.com.
We’re a hosted version of the open source software. Here, you can start a blog or build a website in seconds without any technical knowledge.”