After you develop your application, you need to distribute this application to other organizations. There are scenarios where you need to deploy the same set of components (an application) to multiple organizations. Most probably, these many organizations are outside of your company and you have to access the source and target organizations with high-level permissions. Packages are the medium for this type of deployment. A package is a collection of the Force.com platform components such as apps, objects, reports, or e-mail templates. These packages can be uploaded to be shared with others privately or posted on the Force.com AppExchange to be shared publicly. Mainly, there are two types of packages:
Managed packages
Unmanaged packages
The following diagram illustrates the concept between managed and unmanaged packages:
This diagram will be explained under the next two sub sections.