Recycled glass is known as cullet. Glass bottles or any other glass containers (all glass is treated the same) are first put into a recycling bin or bottle bank - these usally have different compartments for clear, green and brown glass but a few are mixed (as are the special glass recycling household bins which some councils now provide to homes.) For mixed glass, there are recycling plants with special facilities for separating the different coloured glass.

Generally, the glass is inspected and cleaned to remove everything non-glass from it - such as metal or plastic parts, paper labels, metal lids from bottles etc. It is then mixed with the other raw materials which are used for making glass - sand, limestone and soda ash, among others. Then it gets made into new bottles or other containers and used again. Glass can be used as often as you like and it will still be usable.

You can learn exactly how the process works here.