What's a therian?

Well, simply put, a therian is someone who spiritually or psychologically identifies themselves as an earthly, non-human animal. You may of heard of otherkin, whom are basically the same, but with non-earthly non-humans. Now, what is "earthly" can be up to debate by certain individuals, such as some people being dragon therians instead of dragon otherkin as they personally believe dragons are earthly (or simply don't know the difference). Personally, I disagree, but to each their own, I guess.

If you're a therian, what are you?

I am a dog therian, much more specifically a samoyed. This is both spiritual and psychological (the psychological effects are directly at fault of the spirituality). Even more specifically, I remember being a sled dog. So, as you would expect, the average "puppyposting" would not appeal to me. I would rather sneak into a group of wolves eating raw meat, gnawing on bones, and living in filth, than be stuck in a group of the puppy people.

Photo is of the Chinookwind Samoyed Sled Team at Ridgway, Colorado (in 2004 at the latest) from here.

I am otherkin (also spiritual, but with much less psychological effect) as well, and in simple terms, a dragon that is similar to an eastern dragon, but has some features of a western one as well, such as hind legs and wings. I have found no other dragonkin that looks close enough to how I remember my own self, so I have dubbed my species as dracoarcticians (or dracoarticians, when I'm stupid).
Here are some examples of dracoarcticians:

The first one is me specifically (note the antlers), second is just an average dracoarctician.

You know you're a human, right?

I am perfectly aware of that. I am aware in the way a transsexual is aware of their natal sex, and I bear a very similar, but not as extreme, hatred for my own natal species! I guess being human has its advantages, however, such as language, opposable thumbs, society (sometimes), and computers. If I weren't forced to be a human, this site wouldn't exist. None of my problems probably would either, but you could never prove it as I couldn't speak. If I had a choice to be a human or a dog, I would choose dog.

Do you wear masks, tails, ears, etc. and run around on all fours like those kids on TikTok?

Jesus Christ! No, I never have, and I never will. I have deadly species dysmorphia, but it requires a trigger, such as a more animal mindset (I would consider myself a suntherian, but it does get much worse in winter). Wearing a costume of what my soul is qualifies as a trigger. Wearing a mask or tail or anything similar would just remind me I am a human who can never revert to being a dog. Maybe a quadsuit would work, but I'd have to be in it a long while and delude myself a few miles.