Following is a short description on 'Using Drupal':

I have installed a few modules (check http://www.twincling.org/node/625 to install a module) now, which include, Content Construction Kit, Views, Administrator Menu, Devel and Advanced Help. Advanced Help is a module which provides help for step by step usage of the other modules.

First thing that i did is added a role (Administer->User Management->Roles->Add Role), named it Administrator. Then assigned all permissions to that role, so that the Admistrator can do whatever he wants. I assigned myself to that role (Administer->User management->Users->Edit and then tick the corresponding check box).

About the navigation menu to the left,

1. My Account tells you about yourself, letting you edit your details and also shows the content created by you.
2. Create Content contains entries like Blog entry, Book Page, Page, Story,etc. In my case, it contains other entries like Registration Form and Scrap. I created these content types using CCK.

3. Administer contains the following:

a. Content Management:
It contains entries like Content wherein you can publish the blog/story/comments written by users, if they are not published automatically. You can choose whether or not content posted by users are published automatically by selecting/de-selecting the check box at Administer->ContentManagement->ContentTypes->edit(at the corresponding content type)->WorkFlow Settings.
ContentType is another entry here wherein you can add Content Types, edit existing content types and manage fields to add/remove fields. Forms can be created using this option.
Post Settings allow you to specify the no. of posts on the main page. Try adding blogs/stories/Comments and then changing the no. of posts and updates in the main page would contain the corresponding no. of posts, with links to the remaining posts.

b. SiteBuilding:
It contains entries like Blocks which are used to position the various menus/forms at different places. Try creating a menu or a form and place it at different locations.
The Menu entry contains all the Menus in the website and clicking on any of them will allow you to enable/disable/edit/delete menu items in that menu.
The Modules link lists all the modules installed. You can enable/disable any of the modules here.
Themes allow you to use any of the existing themes (including the installed themes)
Views is used to create new views for forms, menus, etc.(Will discuss about it later)

c. SiteConfiguration:
Havent explored this part much, except for clean URLs which allow you to specify whether or not to use clean URLs for your website (Clean URLs do not contain '?q='). Site Maintenance is used to specify whether the site if offine/online.

d. User Management:
Permissions: For every content type, every module, you can specify if each of the roles are permitted to view/edit/create/delete them.
Roles: This allows you to add a new role and edit permissions of existing roles.
Users: This link gives you the list of all users and allows you to edit their details/permissions etc.

e. Reports:
This section shows you the recent log entries of all the activities performed, Available updates for each of the modules and Status Report.

f. Advanced Help and Help:
The advanced help link is provided by the Advanced Help module and provides information regarding the basic uses of each of the contributed modules. The Help link provides help for each of the core modules.

4. Log Out is used to log out from the account.

That's a small description on few of the many options provided by Drupal :)

Regards,
Kartik Nayak.