Drupal terms

Block = areas with specific function (login)

Blocks are the areas on your drupal site where your users do stuff or see stuff. Most modules require blocks in order to be effective and as administrator you get to decide where the blocks show up (sidebar, content area...) and for who (authenticated users, visitors...) and on what pages and how far up the page (weight).

Node = piece of content

Content such as a blog entry or discussion board thread.

Theme = look and feel, css

The css and graphics that create the look-and-feel.

Template = php/html files for page structure

In Drupal the "template" refers the php/html files for your site. Although there are several templating systems, we will be using the one called PHP Template. The most basic of these for your site is page.tpl.php which controls the whole page. Other xxx.tpl.php may be used to control parts of the page such as block.tpl.php. Templates decide things like whether you have navigation, login, breadcrumbs etc on the page

Module = functionality

Modules are plugins that add specific functionality to your site. Core modules are part of the official Drupal application, others, called Contributed since most are developed by volunteers, are optional. Some modules build on other modules, so when you choose a module you also have to download the modules it requires.

See list of drupal modules. Note that you need to log in to take full advantage of this list.

There's an even better service for reviewing/downloading modules at drupalmodules.com