Ok so now we've reached the 2010 SharePoint version milestone, let's see how we got here:
SharePoint last 3 major versions: 2003 -> 2007 -> 2010 (The year doesn't necessary correspond exactly to the year a SharePoint release was made)
The light or free version:
STS -> WSS -> SharePoint Foundation
The paid server version:
SPS -> MOSS -> SharePoint Server
Version 2 or v2 (2003) of SharePoint often refers to STS, SPS ie. SharePoint Team Services and SharePoint Portal Server
Version 3 or v3 (2007) of SharePoint often refers to WSS, MOSS ie. Windows SharePoint Services and Microsoft Office SharePoint Server
Although not yet widely recognised as v4, SharePoint 2010 could be seen as version 4.
in v3 (2007) we refer to the Hive as the following SharePoint system folder: %PROGRAMFILES%\Common Files\Microsoft Shared\Web Server Extensions\12
in v4 (2010) the SharePoint system folder is referred to as the SharePoint root: %PROGRAMFILES%\Common Files\Microsoft Shared\Web Server Extensions\14