Tutorial: Managing Posts, Pages and Categories
Manage -> Posts and Manage -> Pages
Both of these sections are virtually the same. It lists all your existing posts and drafts in the Posts section and your existing pages, be they published or not, in the Pages section. Here you can view the post/page, edit or remove them.
Manage -> Categories
Under Manage Categories you can add new categories or edit and remove the existing categories. Categories can be top level or a child of a parent category. When you remove a category the posts under that category are moved to the default category automatically.
The Manage Categories page also lists link categories along with the post categories. This is a new feature since version 2.1, which is a shame as it’s a lot more confusing combining these categories together.