While plastic was originally made from petroleum, it is now also made from various plants (PLAs) and other plastics (recycled plastics).
It's relatively easy to find out what plastic products are made of and how they are made, especially if they are made of recycled plastics. The question that is generally dodged is whether the resulting plastic is recyclable. Often the answer is no, or not easily. This is slowly changing as more and more innovation becomes business in recycling, but it's slow.It's worth bearing in mind that if you really need a particular product, even if it isn't recyclable, that it's better to buy one that contains recycled materials than virgin plastic.
Most plastics - around 90% of plastic produced globally, fall into one of six categories (plus one): PET/PETE, HDPE, LDPE, PP, PVC, PS, and OTHER and that is how they are universally categorised. When you see a number on a plastic container, it is telling you what kind of plastic your container is.
Plastics 1 & 2 are recyclable in your council bin always. Plastics 3, 4 & 5 are generally recyclable in your council bin, but you need to check. (Soft plastics pretty much never are.) Plastics 6 & & are not recyclable in your council bin.
No real definition exists for Micro-plastics, but they are most often broken bits of bigger plastics and sometimes microbeads or glitter. They are known generally to be synthetic polymers made from petrochemicals and are less than 5mm in length or diameter. They aren't really the kind of thing you recycle, but they are the kind of thing you avoid creating in the first place by not consuming things that create them.
Soft plastics are any plastic - generally packaging or shopping bags that can be scrunched into a ball in your hand. These can be recycled via REDCycle at pretty much any Coles or Woolworths store. Look for the bins at the front of the store. (Packaging can be from anywhere and includes anything soft, even dog food bags.)
Polylactic Acid (PLA) plastics are made from biomass or plants rather than oil. It's typically compostable or degradable, but not biodegradable. It will only break down under specified conditions in an industrial composting facility. You cannot put PLA plastics in your recycling as they contaminate other plastics. PLA marketing writes itself - plant based, degradable, industrial composting - but none of that is useful. It's still plastic and worse than most plastics because access to appropriate facilities is low and you can't add it to recycle bins.
Compostable plastics are made from things like starch and will break down in your home compost - and not into microplastics. They feel softer and a little different to other plastics and don't last forever so keep them somewhere cool. You can get bin liners from people like Biobag and courier bags from people like Better Packaging. When you purchase something that claims to be compostable, only buy it if it is Home Compostable, not Industrially Compostable unless you have access to an industrial facility.
The more traditional plastic is coded RPET (Recycled polyethylene terephthalate [PETE/PET) and is still the world's most recycled plastic. Econyl® is a recycled plastic yarn, a regenerated nylon, made from (nylon) ghost nets fished out of the ocean and other consumer waste, common in swimwear and active wear.
Both these fabrics are plastics. Polyester is a PET or RPET plastic. Nylon is a bit more confusing, especially as it has a bunch of it's own numbers that tell you what kind of Nylon it is. Nylon is an OTHER plastic. At this point, neither product is generally recyclable, but businesses like Blocktexx are working to change that. Meantime, recycle at the Op shop or through friends.