Microblogging uses short posts or status updates that can contain text, images, and internet links. Twitter is an example of a microblogging platform and while Mastodon is intentionally not an exact Twitter clone that is the closest example of how Mastodon looks and works.
The Fediverse (a portmanteau of “federation” and “universe”) is an interconnected group of servers (instances) that form a decentralized social media network.
No matter which instance you sign up with you can connect to users on any other Mastodon instance. Think of it like email – if you have a Yahoo email account you can email someone with a Google address.
This decentralization means that no one person or company controls Mastodon or the Fediverse. Each instance (e.g. norcal.social) has it’s own rules about who can sign up and what content is allowed. There is no corporate ownership, no advertising, and no algorithm deciding for you what you see.
There are other platforms on the Fediverse besides Mastodon. Examples include Pixelfed which looks and works a lot like Instagram and Friendica which is more like facebook. Any account on any instance on any of these platforms can connect with any of the others.
Here is an informational video put out by the Mastodon developers: