When we are talking about customizations for Microsoft Dynamics CRM, one of the most important concepts is the solution. The solution is a container of all the configurations and customizations. This packaging method allows customizers to track customizations, export and reimport them into other environments, as well as group specific sets of customizations by functionality or project cycle. Managing solutions is an aspect that should not be taken lightly, as down the road, a properly designed solution packaging model can help a lot, or an incorrect one can create difficulties.
Using solutions is a best practice. While you can implement customizations without using solutions, these customizations will be merged into the base solutions and you will not be able to export the customizations separately from the core elements of the platform.
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For a comprehensive description of solutions, you can refer to the MSDN documentation available at http://msdn.microsoft.com/en-gb/library/gg334576...