If you've worked with a chat agent, you've basically worked with context. Context is the input that you give the agent that will dictate how you want the response to be. The AI Assistant already have different UI settings for adding context, for instance how long a generated text should be or the style of the text. With additional context you can add additional context that will be used a cross your solution.
In the case of adding additional context in code, there's more freedom of dynamically being able to set the context, which makes it possible to set different contexts for instance for different sites or parts of sites. An example of how clients is using this is to be able to tweak how alt texts are being generated based on what site/brand the images are used on.