I got it from the Discovery kit of sharepoint  portal...I have downloaded
the kit from the Mic.site.. which will give you more technical
explanation....
*SharePoint portal  Server 2003: Additional Enterprise Capabilities*

Enterprise Application Integration

· Single Sign-On services

· BizTalk integration

Audience Targeting of Content

· Web Parts and Web Part Content

· site  directory listings

· News and Topics areas and listings

· News Areas Web Part

· News Web Part

· Topic Assistant Suggestions Web Part

· Custom portal areas and listings

· Area Details Web Part

· Area Contents Web Part

· Grouped Listings

User Profiles and My Site Personal Sites

· Built-in Active Directory Synchronization

· Custom user profile properties

· Picture

· Personal and Public My Site views with (optional) full SharePoint site
capabilities

· Documents by Me Web Part

Personalized Web Parts

· My Links and Links for You

· My News and News for You

· My Alerts Summary

· My Calendar, My Inbox, My Mail Folder and My Tasks Exchange Web Parts

· My Workspace Sites

· Your Recent Documents

Centrally Administered Inter-Portal Shared Services

· Search

· Notifications

· Audience Targeting

· User Profiles

· Single Sign-On

Enterprise Full-Text and Property Indexing and Search

· SharePoint sites

· Intranet sites

· Internet sites

· Lotus Notes databases

· Exchange public folders

· SharePoint Portal server  portal areas and listings including News and
Topics

· SharePoint Portal Server site directory

· People and their Knowledge and Expertise

· User Profile information

· My Site personal sites

· SQL Server 2000 databases

· Active Directory

· Automatic content categorization

· Custom protocol handlers for proprietary content sources

SharePoint Portal Server Web Parts

· More Links

Taxonomy-based SharePoint Site Creation and Site Directory

Alerts

· Search results

· My Site personal sites

· Central management of all alerts

*Windows SharePoint Services: Base Capabilities*

SharePoint sites

· User-driven site creation

· Site templates

· Team Site

· Document Workspace

· Meeting Workspaces

· Blank Site

· Simple List Templates

· Links

· Announcement

· Contacts

· Events

· Tasks

· Issues

· Advanced List Templates

· General Discussion

· Document Library

· Picture Library

· XML Forms Library

· Survey

· Custom Lists

· Web Part Pages and Web Part Zones

· Web Parts

· Announcements

· Contacts

· Content Editor

· Events

· Form

· General Discussion

· Image

· Links

· Members

· Page Viewer

· Document Library

· Tasks

· XML

· Office 2003 Integration

· Microsoft Access

· Database integration

· Microsoft Excel

· Spreadsheet import & export

· Spreadsheet copy & paste

· Live Web query

· Microsoft FrontPage

· User interface customization

· Data integration

· Microsoft InfoPath

· Smart client XML forms

· Microsoft Outlook

· Contact list import

· Contact list synchronization

· Calendar synchronization

· Microsoft Word

· Check-in/checkout

· Version history

· Editing

Alerts

· Lists (all types)

· Libraries (all types)

Search

· Single collections of SharePoint sites

The best guide is probably this one -
www.microsoft.com/.../relationship.mspx

The bottom line is WSS is included in Windows Server 2003 and is focused on
group collaboration - document sharing, meetings, etc. portal  is a product on
its own, is built using WSS as the platform, but it focsed on more tradiitional
portal activities (exposing information to large, targetted audiences,
enterprised search, application integration, etc).