What is WordPress?
WordPress is a free, open source content management system (CMS). It’s a software that allows people to create, organize, and update websites without having to manually code every page. WordPress actually started as a blogging platform, however, it has grown into something much more than that now. It has evolved to be used as full content management system and so much more through the thousands of plugins, widgets and themes. WordPress is currently powering more than 26% of the web.
The most important part of WordPress is that it comes in two forms—WordPress.com and WordPress.org. WordPress.com is a blog hosting service that allows users to setup a free website that operates on custom version (limited) of the WordPress software. And then there is WordPress.org, a software with which you can do just about anything without any limitations. In simple words, WordPress.org is basically the home of the open source WordPress software. Most importantly, WordPress is an all-in-one feature-packed website platform, it can do just anything!
Do your themes work on WordPress.com websites?
WordPress.com did not allowed to upload your theme, but now by purchasing WordPress.com Business plan for your blog you are allowed to upload your own theme via Appearance feature. Go to this link: https://en.support.wordpress.com/themes/uploading-setting-up-custom-themes/ for more details about Uploading and Setting up Custom Themes.
What are WordPress themes?
According to WordPress.org, themes are collections of files “that work together to produce a graphical interface with an underlying unifying design for a weblog.” In simple, a WordPress theme is what controls the functionality, the look, and the feel of a WordPress website. WordPress themes come in a variety of flavors, from basic, free themes to more complex, premium themes. The key takeaway about WordPress themes for any beginner is that at any moment a WordPress website’s theme may be changed without adversely affecting the actual content of the website.