From what I understand, emo fashion is based on teen fashion of the 2000's to early 2010's. So, emo is mostly comprised of skinny jeans (ripped or not ripped), T-shirts, Converse or Vans, and accessories like arm warmers, chokers, layered necklaces, etc. The T-shirts mostly being band T-shirts, T-shirts of popular characters from movies and shows, and I think sometimes slogan T-shirts, depending on what the slogan is exactly. Some emo people also wear a bit of makeup. When emo was first started, I think it was mainly simple black eyeliner and maybe black lipstick, although in recent years some people like to add more to the emo makeup look, like more complicated eyeliner. There's also of course the hair, emo hair tends to have a lot of layers and side swept bangs, it can also be of any length. Emo hair for the most part, is dyed black, but it can have some steaks of color in it.
On the other hand, there's punk. Admittedly, I don't know too much about punk, but I have a basic idea of it. Punk is much older than emo from what I understand, and I believe it was started in the 70s. Punk was originally built off of the idea of cheap, affordable, DIY fashion. This is mainly because punk started as being anti-big corporation and they believed in supporting smaller businesses. Punk people wear a lot of DIY-like clothing, they tend to make patches and put them on jackets and pants. They also do the same thing with safety pins. The whole safety pins thing is because wearing safety pins symbolizes that you're a "safe" person, meaning you accept people no matter their gender, sexuality, race, etc. The patches that punk people make tend to have messages on them, like being anti-Nazi, anti-police, etc. Punk fashion, outside of patches and safety pins, tends to include semi-baggy pants (ripped or not ripped), leather jackets, denim vests, boots with laces, and I think plain T-shirts. Some punk people also follow a lace code, which I can't quite remember, but it's worth noting. I don't think punk people tend to wear makeup, but I could be wrong on that. For punk hair, most of the time its styled into liberty spikes. Liberty spikes are made by using hair spray on a piece of hair enough to the point where it sticks up or outwards into a spike shape. The spikes can be put into any formation, from what I've seen. It also seems like Punk hair can be dyed whatever color.
While emo and punk do have a few similarities, there's definitely a lot of differences between the two. Sorry for the long ramble lol- I'm somewhat passionate about fashion lol-