The Beginner's Drupal Administration Series
The 'Structure' admin menu section is the place where you add/edit/delete blocks, content types, menus and terms for your site! It has all the building blocks needed to set up a site's structure. Let's go over those sections one-by-one.
The blocks section on your site looks like this:
It displays the regions you have on your site in the left (different for each theme) and which blocks appear in which regions under those regions. If your site uses the Context module (highly recommended), however, it may appear like no blocks are enabled for any regions, when they are actually getting placed through the Context module.
To move blocks around, you can select and hold one of the 'handlebar' icons to the left of a block and simply drag-and-drop it into the region you want. You may see block weights, instead of block handlebars (like below). Which interface you see is controlled by the circled link in the screenshot. Toggle between the two as you please!
Configure a block (link to the right) to specify which user roles or specific pages you want it to appear for; otherwise, it will appear globally on your entire site! The block configuration screen allows you to specify which specific pages (add them as 'node/13', etc.), which content types, which roles or which specific users you want the blocks to appear for:
Go here to create new content types or manage the content types that already exist on your site. To understand why your site may need different content types, let's explore an example. Say you want to have pages that display each of your staff's bios, along with an image, title, phone number and short bio for each person. You may start off by just creating a regular ol' page for each person and formatting it to look exactly the same way: everyone's photo is aligned to the top left, everyone's title uses the same font and size, etc.
Why create new content types?
However, if you choose to reorder these fields later (so the image appears after the bio or something like that), and if you're not using separate fields that you can easily order (they are all together in the page's 'body' field), you'd have to go into each bio page separately and re-organize the display one-by-one! Or, if you have a lot of content editors on the site who are formatting these pages a little differently, you may want to create a special content type that has the image, title, bio, phone, etc. as separate fields that you have ordered and styled properly. This way, the editors don't have to make these decisions themselves. So that's what content types do - for each, you choose what types of fields an editor has to enter, which are mandatory or optional, how they are ordered, and once you get into theming (a later tutorial), how they are styled in that node's display (e.g. the job title to always appear in grey text and in caps). Here is a good Lullabot video on creating new content types in Drupal 7 Finally - as you can see on the video, you can also manage settings relating to your content types, such as whether comments are enabled, whether editors can hook up nodes from that content type to the menu, etc.
The menus section shows you all the menus you have on your site. You can add new menus, or edit/delete the existing ones.
Taxonomy (terms, tags)
The taxonomy section of your Drupal site is used to administer the vocabularies, and their related terms, on your site. Terms are grouped into vocabularies. So, for example, if you want to tag nodes on your site with their location, such as 'North Carolina', 'California', etc, you could group those terms into a vocabulary called 'State', so they are not mixed with other, unrelated terms.
When you click on the 'Taxonomy' menu item on your drupal admin screen, what you see is the vocabularies. You can add new terms, edit or delete existing ones, or edit the vocabulary (i.e., change its name & description).
Why use taxonomy?
With the functionality Drupal has right out-of-the-box, you can use the terms on your site to tag posts, so users can find related content easily. For example, if you tag two different posts with the 'East' region term, a user who is reading one of the posts, and sees that tag displayed, can click on it to see all your other posts related to that location. However, if you use the Views module on your site, you can use tags in much more interesting ways to route where and how tagged content is displayed on your site. Finally - after you've added a vocabulary and all the terms it contains, you have to add a 'Term Reference' field to the content types you want to be able to tag with that vocabulary. New vocabularies will not automatically just show up on all your content types - you have to add them where you want them.