How is the custom add-ons integrated in Sharepoint 2010?

How is the custom add-ons integrated in Sharepoint 2010?

- Custom add-ons are the features and solutions in Sharepoint 2010 and provide customized code that can be installed on a farm level.

- Custom add-ons use Global Assembly Cache (GAC) on the server but it sometimes become difficult to deploy.

- These are also integrated as Sand-boxed solutions that are being uploaded by the end users.

- Sand-boxed solutions consists of permissions to upload the solutions through the easy to use the web-interface.

- The solutions are very secure and restricted to allow only few people that pass the authentication and it is governed by farm infrastructure.