@Sangeeta Well, the 'existing on Mastodon' concept should be reformulated.
Masrodon in an open technology shared by thousands of independent social networks (the Instances) that everyone can install ob his server freely. All this Instances are connected together. Mastodon.social, the one you're on, is just one of them.
So there is not a single entity called Mastodon but a Galaxy of independent Stars (Instances).
Also, every Instance can decide to block other ones.
Those Instances will continue to exist, but wouldn't interact anymore with the ones who blocked them.
Is like saying that Yahoo blocked every interactiin with Gmail. They will be both on the 'email Galaxy' but Yahoo users will not interact anymore with the Gmail ones.