There are thousands, of small communities that live within the Mastodon system.
Each one is independent and unique, but they can all talk to one another.
These communities are called "INSTANCES".
Instead at any domain that runs Mastodon is called an instance and you can join any instance!
Think about various email providers.
Gmail, Yahoo, Outlook etc.
U can create an email address is firstname.lastname@example.org or email@example.com.
Here xyz is the username. We know that both email address belong to different persons or same persons.
They can send email to each other.
Given screenshots to understand how the steps are!
My QN is are you confused with Gmail and Yahoo mail?
You are too much used to Twitterverse & you expect a single server.
Here it work differently
Same is the case is with Facebook.
But here your ID is
Exactly like email, ie, firstname.lastname@example.org
Here my ID is email@example.com
My instance name is also needed to identify
Are you confused with various email addresses with different service providers?
Is it necessary all should have same domain address to communicate?
Here no centralised server or a monopoly corporation, each instance is a community which is moderated by human admins, not by bots run on AI ;)
But that choice is not going to curtail your freedom to follow people from other instances or getting followers from other instances.
Otherwise forget the above steps.
I will guide you how to join other instances in next tweet.
Here, Eugen's TOOTS and BOOSTS are in my HOME TL.
All this exercise can be done through your mobile browser or desktop browser.
2. Here on the column provide your #mastodon ID (here firstname.lastname@example.org), then click "Proceed to follow"
3. It's done, now by clicking "Go to Web" you can go to HOME or see "User's Profile
You need to click individual toot (tweet) to see the number of boosts and favourites
I provide the equivalent twitter term in bracket
Here your toot can have 500 characters instead of 280 of twitter.
In your toot window if you click third button you will get 4 choices
1. Public - visible in all public TLs
2. Unlisted - not visible in local/federated TLs, but visible in your profile
3. Followers only
4. Direct to user
So you can play with it to suit your choices
But there are third party legacy apps availabld in android and iOS. Also web apps and desktop apps available.
All of these require "authorization" through web browser.