So with no further ado…
1. Your site is at something.wordpress.com
That’s unless you’ve paid WordPress.com to allow you to use a custom domain name. If you have then that’s another clue, as owners of WordPress.org websites don’t need to pay WordPress to use their own domain names (but you’d still need to register a domain name with someone else).
2. Your website admin page looks like this
3. Or if you’re accessing the old WordPress.com dashboard this logo will link to wordpress.com
4. You see the WordPress admin bar
If you don’t have access the website’s admin you can simply log in to WordPress.com (creating an account is free) and browse to the website. If it’s a WordPress.com website you’ll see this visitor bar at the top of the website, allowing you to add the site to your WordPress reader favourites, among other things.