The Windows SharePoint Services solution framework provides a way to bundle all the components for extending Windows SharePoint Services in a new file that is called a solution file. A solution file has a .CAB-based format but a .WSP extension. A solution is a deployable, reusable package that can contain a set of Features, site definitions, and assemblies that apply to sites, and that you can enable or disable individually. You can use the solution file to deploy the contents of a Web Part package, including assemblies, class resources, .dwp files, and other package components.
The Windows SharePoint Services solution framework is built upon the functionality provided in Windows SharePoint Services 2.0 by site and list definitions, .stp files, and .fwp files. It supersedes the functionality provided in Windows SharePoint Services 2.0 by Web Part packages (.wpp files). For backward compatibility, Web Part packages are supported in the Windows SharePoint Services 3.0 solution framework. However, it is recommended that you deploy Web Parts through solution files (.wsp files) because the solution framework is more robust and can be used to deploy more types of entities than Web Part packages.
Benefits of the Solution Framework
The solution framework provides the following advantages:
A unified infrastructure for deploying solutions. For ease in making changes to site functionality, Web sites do not need to be bound permanently to the Features and functionality of the sites when they were first created. By using Features, you can easily enable or disable functionality at a specified scope, as well as convert sites from one type to another.
A Feature is a collection of SharePoint elements that helps a user accomplish a particular goal or task. For more information, see Working with Features.
Integrated deployment. Solutions enable developers and administrators to easily install files on the front-end Web servers in a server farm. Windows SharePoint Services can package all your Windows SharePoint Services entities as one file, add the file to the solution store, and deploy it to the front-end Web servers.
The solution framework allows you to do the following:
Deploy new solutions and upgrade existing solutions across the farm.
Synchronize a front-end Web server so that its state is consistent with the state of other servers in the farm.
The solution framework supports deployment of solutions to both front-end Web servers and to application servers configured in the farm.
For more information, see Deploying a Solution.
Unified localization. There are central facilities for specifying localization settings, as well as ways to specify localizable token databases.
For more information, see Localizing a Solution.