Recycling means collecting used materials and processing them so that they can be made into new products instead of being thrown away. The new product does not have to be the same as the old one. Drinks bottles are made from a polymer called PET. Used bottles can be collected, sorted by type of plastic, washed and shredded into flakes. The flakes are melted and drawn out into thin fibres, and the fibres are spun into polyester fleece for jackets and blankets.
PET is made from crude oil, which is a finite resource. Using old bottles as the raw material means less crude oil is needed. Making fleece from recycled flakes also uses less energy than making new polymer from crude oil. PET does not rot, so every bottle that is not recycled stays in landfill for a very long time.
A recycling process is viable when it makes sense in practice. This happens when the cost of collecting, sorting and processing the waste is lower than the value of the product that is made from it, and when there is a market of people who want to buy that product.