This isn’t always a simple answer. Every country can define waste in its own way but in the UK (and Europe) waste is defined as “any substance or object which the holder discards or intends or is required to discard”

Again, this can be defined differently by different countries but is generally a subset of waste that has properties that make them harmful to your health, or can negatively impact the environment

Waste is typically (but not always) something that people don’t want and it can be expensive to deal with properly. However, if you don’t manage hazardous waste properly then it can get to places where it can be dangerous. Sometimes without people even noticing. once its in the wrong place, it could result in health problems, environmental issues, or in extreme cases, even death!