Explanation:

Hopefully most people know that MOSS is a superset of WSS. In other words, MOSS takes the foundation laid by WSS v3.0 and expands upon it, creating features that sit on top of it, utilize the core WSS framework, and extend it in such a way that is beneficial to larger companies, enterprise deployments, and portal scenarios. The following is a list of things that MOSS provides that WSS v3.0 does not. I figured it would be a waste of text to show the features that the two have in common, or the places in which MOSS re-uses WSS functionality without change or enhancement.

Features included in MOSS that are not included in WSS:

• Social Networking
  • MOSS provides social networking features, including social networking Web Parts and profile linking. MOSS allows you to establish peer links between colleagues and identify hierarchical relationships. These relationships can be published on My Site pages and traversed wherever your personal profile appears on a site/web part.
• My Site
  • MOSS provides the ability for individual users of a portal to create their own "My Site". My Site is essentially a home page / landing page designed to provide you with a starting point through which to access content that you own and content that might be relevant to you. This is also the place where your personal profile is published. You can also create shared and private image and document libraries, as well as your own pages and publication areas. You can also create your own personal blog on your My Site. Some people think of a My Site as a "professional version of a MySpace site". I'll leave it up to you as to whether you agree with that comparison or not.
• Site Directory
  • MOSS provides a new site template called "Site Directory". When you create your first portal via MOSS, it comes with a Site Directory. This site template is designed specifically for tracking links to sites, displaying site maps and site navigation lists, as well as searching through the site directory. With a Site Directory in your portal, you will be asked if you want to publish a link to your new site every time you create a new site within the portal, regardless of its depth within the hierarchy. This single feature is, in my opinion, absolutely required for any kind of Intranet deployment of SharePoint. And yes, that means I think MOSS is a requirement for any real Intranet deployment of SharePoint on any kind of meaningful scale.
• User Profiles
  • MOSS allows for Active Directory-integrated user profiles. It also provides security around profile properties. In other words, you can have information in your profile that is visible only to you, visible to your superiors, visible to your colleagues, etc. You can control what audience can see which user profile properties, and much more than that. Again, I feel that the enhanced user profile store features of MOSS make it almost a necessity, not an add-on.
• Site Manager
  • MOSS provides for an easy drag-and-drop interface for managing navigation bars, navigation strips, portal hierarchy information, and much more. In general, managing sites, site hierarchies, and hierchical site content is much easier (and in some cases simply made possible) with MOSS.
• Portal or "Enterprise" templates
  • MOSS comes with new templates for a Portal Site (the default root-level site template of a portal site), Document Center, Search Center, Report Center (available only in the SharePoint 2007 Enterprise SKU, not Standard), and Site Directory.
• Search
  • MOSS uses an enhanced relevance algorithm for its search engine, and is able to crawl content from multiple sites within an enterprise, as well as non-sharepoint web sites. In short, the MOSS search engine is a powerful enterprise search engine with a relevance algorithm, while the WSS site-local search engine is actually pretty useless beyond simple "dumb keyword" search.
• Knowledge Network / People Search
  • MOSS provides an enhanced "people search" tool that can be used to try and mine hidden relationship data and show you people related to knowledge. For example, if my name is splattered all over dozens of websites that contain C#-related content, the idea is that MOSS will show you my name and profile in response to a search for people related to C#, and suggest me as a local expert.
• Business Data Catalog / Business Data Search
  • I think this is quite possibly one of the most important features in MOSS. It allows you to extend SharePoint data by integrating Business Data from external sources such as Web Services or Relational Databases. This allows you to do things like display SAP data within your SharePoint portal, or add a column to a Requirements Document stored in SharePoint that points to data stored in a Requirements Management tool elsewhere in your enterprise. The possiblities for the BDC are limitless, and I really think every single SharePoint 2007 developer needs to learn this stuff in and out (this is reflected in the extensive coverage of the BDC in our upcoming book, SharePoint 2007 Development Unleashed .)
• Document Workflow
  • I can't stress how unbelievaly powerful this feature is. You can use the stock (included "in the box") workflows such as collecting feedback and performing a review of a document, or you can create your own workflows using a custom Workflow designer to create powerful (and really, really handy) workflows around specific types of documents like Whitepapers or magazine article submissions, chapter submissions (hint, nudge), etc.
• Excel Services
  • MOSS provides the ability, through its Shared Services facility, to have what amounts to an Excel server. This provides the ability to display the contents of excel spreadsheets within web parts, and to selectively allow editing of secured regions of that spreadsheet, including evaluation of formulae contained within the sheet and having the results display in real-time. There is also a UI-less version of this where you can access a stored central spreadsheet via webservices, establish a "session", and programmatically feed data into the sheet and get formula-calculated values out of the sheet - all without interfering with other people using the same centrally located spreadsheet. The impact to businesses that do anything at all with Excel is huge.