A summary message:
Unlike the main screen, in most templates there is a message at the top of the page saying:"Showing newest posts with label WHAT-EVER-YOU-CHOSE. Show older posts"
Or if there are no published posts with the selected Label, the message is slightly different. Some people change their template to customise or remove this message: Chuck in The Real Blogger Status has written an excellent description of how to do this.
What Labels aren't - but appear to be
Many people think that Labels are a way of actually putting Posts into pages. However the Posts aren't actually moved around. The labels-screen is just a way of viewing a smaller-than-usual group of Posts, and can make it look like you have put your posts into sub-pages.Making multi-level categories
Currently, Blogger only supports one level of grouping. The only way you can make sub-groups of Labels is to add two categories to each post - one for the "major" category, and one for the "minor" categoryFor example you might use labels like these
Each post would need to have at least one label from the major category, and one from the minor categories.
Major category: Minor categories: Recipes: Sweet, Savory, Wheat-free Party-games: ice-breaker, run-around, silent, outdoor Music: lively, soft & gentle, traditional, instrumental
If you do this, you need to be clever about adding two levels of gadget, with only a selected group of labels shown in each gadget. You might even need to edit your template, to only show certain gadgets in certain situations.