There are 3 main areas known as pillars to focus on environment, social and economic.
The use of earth resources in a way that they have enough time for earth to replace them as we use them.
Economic sustainability is the practice of conserving natural and financial resources to create long-term financial stability. Its about the continue access of the economy for all people.
When all people have the ability to get the resources and economic access to get what they need while not facing any exploitation or discrimination of any kind.
Unfortunately, Social Sustainability is still one of the most under-gauged aspect of sustainable development.