As it uses the ActivityPub protocol, you can follow and interact with accounts on Mastodon etc from Friendica, and vice versa.
You can also follow RSS feeds as if they were Fediverse accounts, and when an RSS item is published on that feed it will appear in your timeline as if it's a Fediverse post.
You can write very long posts on Friendica, you don't have to worry about character limits.
You can use Friendica accounts through the FediLab app, available on @fdroidorg and Google Play.
You can follow the latest news about Friendica on its official blog at @news