Here you'll find a (hopefully) handy index to the content on Hastily Written. There are two somewhat clear ways to mark posts. Tags and Categories.
Tags are about the content of a post. In order to not clutter up the tag cloud, for brief posts, especially if it's just an instagram shot, I don't tag each pen or ink in them. That way reliably if you click on TWSBI it will be interesting content about that manufacturer. If you just want to look at some lovely pen p0rn, the instagram tag has a huge range of pens to drool over.
Categories are about the post type. Descriptions are below, and the links will take you to a page with all posts of that category.
Reviews - these are where I talk about pens or ink or paper at length, focusing on what I like and don't, whether it clicked with me, etc.
Essays - less focused than a review, about pens in general, or musings on using them, etc. They may contain some review like content, but are a little more free-floating.
Meta - something focused on the site itself, updates to lists, schedule changes, etc.
Brief - for things like Ink Drop write-ups, posts from instagram, etc. Short posts, probably picture heavy, fun things when I'm in between larger reviews or essays.