Hubski is like a mix between Reddit and Twitter. Instead of default subreddits, you get the option to follow tags. For example, #gaming is the gaming tag, and #reddit is the reddit tag. To link a tag in a post, simply surround a word with hashes (#).
When creating a post, you can assign it to up to two tags at a time and the community can choose to assign a third tag to the post; although those were the rules when I first signed up and this may have changed since.
Unlike Reddit though, there is no moderation on tags unlike there is with subreddits, no such thing as downvoting (so no brigading here), and the experience is far more tailored to the user.
Two rules which are shared with Reddit and Hubski are no doxxing and no sexualised content of minors, so don't expect to see jailbait here...