Gmail is an email provider, and so is protonmail. They are two companies providing email services. And you can communicate between the two email services by sending emails. Both email providers have their own rules and regulations you have to follow because they are run by different people in different places/countries.
Lemmy is similar. Each Lemmy instance provider is run by different people in different places/countries. When you make a comment or post on one instance, it automatically sends your message/post to the other Lemmy providers/instances (if they don’t block the federation). You have to follow the rules of the provider/instance you join, just like for email providers.
Choosing a Lemmy provider/instance based on location or theme is the most common. Also, it’s recommended to not choose the most popular instance, because that would defeat the purpose of federation if everyone is in one place, like reddit (one company, one location, one rule set for the entire platform).
Gmail is an email provider, and so is protonmail. They are two companies providing email services. And you can communicate between the two email services by sending emails. Both email providers have their own rules and regulations you have to follow because they are run by different people in different places/countries.
Lemmy is similar. Each Lemmy instance provider is run by different people in different places/countries. When you make a comment or post on one instance, it automatically sends your message/post to the other Lemmy providers/instances (if they don’t block the federation). You have to follow the rules of the provider/instance you join, just like for email providers.
Choosing a Lemmy provider/instance based on location or theme is the most common. Also, it’s recommended to not choose the most popular instance, because that would defeat the purpose of federation if everyone is in one place, like reddit (one company, one location, one rule set for the entire platform).