A permalink is the link to an individual blog post. These are important because if you ever need to link to an exact blog entry (e.g., as part of a carnival), you use the permalink as your link. It's poor blog etiquette not to use the permalink.

If you don't use the permalink, you'll just be linking to your main blog page. The problem with that is that, as you post new blog entries, the newest entry appears at the top of your main blog page and the other entries are pushed down on the page. The entry your readers are looking for may be down at the bottom of the page or already in the archives; your reader has no idea where to find the entry! If they click over to your site expecting to see a specific post related to a carnival and they see a different post, they may not take the time to find the "real" post they're looking for.