difference between Managed and Unmanaged package in salesforce - Salesforce Globe For You

 Packages: Whenever you need to use the app exchange products or whenever you need to deploy components from one org to another,you can use packages.

Package is a collection of related components like apps,tabs,apex classes,visualforce pages etc.

Whenever you need to use app exchange product,the product related components are packaged in a package which you can directly install and use.

you can create a package in one org and can use the package url to install it in other org.

Packages come in 2 flavours.Managed and Unmanaged.

Differences:

you cannot customize(change) the  code or metadata if required in Managed package but you can do that in unManaged package.

If you use Managed package,upgrades happen automatically when new version released but if you use unManaged package,upgrades won't happen automatically.

In Managed package,the components of the package don’t count against the org limits(tab limits,object limits,app limits etc). where as in unManaged,limits count.