Recyclable and compostable are design criteria and attributes specified by brands, institutional buyers, and citizens. They are aspirational attributes, meaning that they hold the potential for recycling or composting at the end of its useful life. The package may or may not be actually recycled or composted.
Recycling and composting are end of life treatment routes. They are related to the two design criteria but not the same thing at all.
Many factors determine whether a recyclable (or compostable) item is actually recycled (or composted). Some of those factors include access to recovery services and facilities (collecting and sorting), the behavior of individual households or other waste generators, available technology to process the materials, format of the package, loss or leakage due to contamination, and quality of the processed material. Just because an item is recyclable does not guarantee it will be recycled.
Further, just as some materials are recyclable and others are not – because they are made of different materials – those different materials may require different feedstocks and industrial processes to produce, and result in different environmental impacts. Just because a material is recyclable or compostable does not guarantee that its production results in lower impacts, or that its impacts are obviated by recycling or composting.