@rufustheduck mastodon.social is basically the generic everyman server that everyone new to the Fediverse signs up to (mostly because it's ran by Mastodon themselves and is pushed by the official app), but this also means it's a firehose of thousands of people speaking all at once with no real sense of organisation or topic, which means it can get quite busy if you're following the Federated feed. Many people therefore suggest doing research into other Mastodon servers that are around, in case another one might be more structured to your specific interests, as you might find it more comfortable to follow, or easier to find others who share the same interests as you.
fedi.tips has a good explanation about the purpose of different servers in the Fediverse. fedi.garden is a good site to help you find a suitable server for you 