Mastodon
What it's for
The X/Twitter alternative: a social network made of thousands of independent servers that talk to each other (the “fediverse”).
Why it matters
No single owner, no algorithm deciding for you, no arbitrary ban by one company. The feed is chronological, with no ads or manipulation.
For whom & when
Everyone. Ideal for information accounts that want a presence no company can cut off.
Install & use
On joinmastodon.org, choose a server (or “instance”) that suits you, then create an account.
Install an app (the official one, or Ivory, Tusky…) and follow accounts: you see the whole fediverse, whatever their server.