Akkoma is a part of the "fediverse"; that means it's a social network with no central authority. You can follow and talk with anyone else that has an account on any other fediverse service, and you can even host your own server if you want.
For those more familiar with the fediverse, Akkoma is a specialised fork of Pleroma.
It is faster-paced in development and aligns itself more closely with Misskey than Pleroma mainline.
It differentiates itself with a focus on custom expression, for example with custom emoji reactions,
or Misskey-Flavoured Markdown.