The Keyword field is available for advanced use cases that are outside of the scope of this article. We do not recommend entering anything here. If you do enter something, it will almost certainly be completely ignored.
The weight field can be used to specify a numerical value that determines how often this particular banner gets displayed relative to the other banners in the same campaign. There is a separate article explaining how to use Banner weights.
The comments field can be used to enter some notes about the banner, for example to record when and what is changed or by who.