Before working in MOSS 2007, we should know about some keywords like SSP, Web Application, Site Collection and Sites.
WSS: Windows SharePoint Services (WSS) is a technology provided as an extension to Microsoft Windows Server 2003 (and above). According to the Product Team, WSS "provides a platform for
collaboration applications, offering a common framework for document management and a common repository for storing documents of all types."
Farm: The farm is the server or set of servers that host SharePoint. Upon installation, roles are assigned to each server in the farm, and services are bound to servers based on roles and expected traffic patterns. The farm is also defined by its connectivity with external services, including Active Directory and Exchange Server. There is one configuration database per farm, and it is administered by any instance of the Share Point Central Administration web application within the farm.
After installation, you can configure here
SharePoint Central Administration -> Operations -> topologies and Services -> Services on server
Shared Services Provider (SSP): A SSP provides a central point for MOSS services, including: the Index Service, the Query Service, profile import and management, audience management, content management logic, the Business Data Catalog, Excel Services, Forms Services, job scheduling, and usage reporting.
To Create or configure SSP:
SharePoint Central Administration->Application Management -> Create or configure this farm's shared services
For different services different databases are used.
Web Application: The web application is the IIS entity where an application pool context is set for SharePoint, and an address (URL) is defined by IP address, port, and/or host header so that each instance of SharePoint can be located with a web browser or mapped to a DNS common name. The web application has a physical web.config file to configure authentication and to mark components as safe, and virtual folders mapped to physical folders that contain ASP.NET files. These physical files are shared among all Share Point web applications hosted in the farm.
To Create or configure web application:
SharePoint Central Administration->Application Management -> Create or extend Web application.
SPSite (Site Collections): A SharePoint site (SPSite) is an object which contains webs (SPWeb). Each SPSite contains resources available to all of the SPWebs it contains, including SharePoint features and special document libraries called galleries. Galleries exist to hold content types, site columns, Site Templates, List Templates, Web Parts, workflows, and master pages.
To Create or Configure Site Collection:
SharePoint Central Administration->Application Management -> SharePoint Site Management-> Create site collection
SPWeb (Site): An SPWeb is a web within a site collection, and each web may contain its own set of child webs. The RootWeb of a site collection provides an interface to manage the resources (e.g., the galleries) of the site collection.
So conclusion is following :