A plastic mailer is a shipping envelope made of synthetic polymer materials, typically polyethylene, that can take hundreds of years to break down in the environment. Plastic mailers are often used for packaging and shipping items due to their durability and water-resistance.

On the other hand, a biodegradable mailer is a shipping envelope made of biodegradable materials that can break down naturally in the environment. These materials are typically made from plant-based or other renewable sources, and they are designed to break down through natural processes like microbial activity or exposure to sunlight.

The main difference between plastic and biodegradable mailers is their environmental impact. Plastic mailers contribute to plastic pollution and can harm wildlife and ecosystems, while biodegradable mailers are designed to break down and leave minimal impact on the environment. Biodegradable mailers can also be composted and returned to the earth as organic matter, which can provide a sustainable alternative to plastic mailers.