It's a shared electron context, it addresses one of the many critiques of electron (that each electron app is an entirely separate instance of Chrome), so each "sketch" while having the capabilities of electron only have the performance impact of a browser tab.
This is especially useful for "utility applications".
Only as much as is the actual application logic and bundled dependencies. Which for most cases is usually a few kilobytes or a megabyte. You can checkout the Quark appstore (https://dash.quarkjs.io/). None of the apps is above 2MB.
This is especially useful for "utility applications".