puppeteer - what makes an execution context the "default" one?

Question

In Chrome's Puppeteer, at ExecutionContextDescription.auxData you can find an object containing the following properties: isDefault, type and frameId

frameId is fairly straightforward to understand, but the other properties doesn't seem documented anywhere. What makes an execution context the default one? Isn't the execution context always just one for each frame at any given time?

Answer 1

From https://github.com/puppeteer/puppeteer/blob/main/docs/api.md#overview :

Frame has at least one execution context - the default execution context - where the frame's JavaScript is executed. A Frame might have additional execution contexts that are associated with extensions.