WordPress vs. WordPress.com
People are often confused about the differences between WordPress and WordPress.com. WordPress is the free, Open Source web publishing software project, owned by no one individual or company. WordPress.com is a hosted blogging service run by a company called Automattic.
WordPress
WordPress (sometimes called “www.ads-software.com” or “self-hosted WordPress” for disambiguation purposes), is software that you can download and install on any web host. It began in 2003 as a fork of b2/cafelog. Licensed by the GPL, you are free to use WordPress without restriction. Sites powered by WordPress may have a “Proudly powered by WordPress” credit, or they may have no credit at all. The absence of any mention of “WordPress.com” is a good indicator that it is a self-hosted WordPress instance).
WordPress.com
WordPress.com (a.k.a. “wpcom” or “WP.com”) is a for-profit hosted blogging service run by Automattic. WordPress.com launched in 2005, and is the largest WordPress install in the world. It is powered by WordPress, with some additional plugins and modifications layered on. Having “.wordpress.com” in the domain of the blog or the presence of a “Blog at WordPress.com” promo message or credits image can be used to determine whether a site is hosted at WordPress.com.
Overlap
What is the overlap between WordPress and WordPress.com? First, Matt Mullenweg is both CEO of Automattic, and co-founder of WordPress. Matt is involved with both WordPress and WordPress.com. Some WordPress contributors are also employees of Automattic. There are many more WordPress contributors, most of which have no connection with WordPress.com.
Development decisions about WordPress are made without specific regard to their impact on WordPress.com. Any special changes that WordPress.com needs are made on that side, by Automattic employees.
Additional resource
This video is an overview of the differences between WordPress and WordPress.com:
FAQ
Automattic’s relationship to WordPress?
Automattic uses WordPress to power WordPress.com, and it contributes back code and time to the WordPress project. It is a symbiotic relationship. It isn’t accurate to say that WordPress is Automattic’s product, or that WordPress came from Automattic. Indeed, the opposite is true — Automattic came from WordPress, and Automattic (through WordPress.com) exists as part of the vast WordPress community and ecosystem.
Why can’t I call WordPress.com just “WordPress”?
Because it isn’t clear what you’re talking about — the Open Source project, or the hosted blogging service. They are distinct, and statements about one aren’t necessarily true about the other. WordPress.com is its name. You wouldn’t call bit.ly, the popular link shortening service, just “bit,” would you?
Why doesn’t Automattic rename WordPress.com to something more distinct?
WordPress.com offers multi-site for free and on very inexpensive plans, has never had any downtime or lost user data since 2005, and has onboarded and introduced hundreds of millions of people to WordPress. Their higher-tier plans offer some of the fastest and most secure WordPress Managed Hosting available anywhere, with full plugin and theme support. That advanced managed platform is now licensed to other hosts through wp.cloud and is raising the bar for the industry. The flavor of WordPress offered by WordPress.com is a huge asset to the brand and adoption of WordPress overall.