Xcode: Project and Target, add resources to target?

I'm building my first app and I'm a bit confused about all the project and target settings. So far I understand that a project can have multiple targets, for example a lite and a full version. So first I'm building my full version and later on adjusting it for the lite one.

My question is now about the resources you add to the targets. So far I've never checked the checkbox "Add to target …" while adding images, fonts etc. Still it works fine. So why or why shouldn't I check this box? And if I need to check it, how can I do this for all the images etc. I've added to the project?

And I think in my resource folder are still some resources I don't need anymore and actually deleted in Xcode (correctly, not just deleting the link basically)..how can I get rid of them?

Solution

When you add a file/resource in Xcode (either using "New File" or "Add File to "), you will see a checkbox for all the targets in your project. You can check the ones that you want to include the new file/resource. For the existing file/resources in xcode, you have following two options:

For your target->Build Phases->Copy Bundle Resources, you can add resources to the target.
Click on the file/resource in project navigator, under "Utility View"->Target Membership, you can select/deselect the targets that need to include/remove this file/resource.

Regarding deleting resources, when you delete a resource or any file in XCode, it will give you options: "Remove Reference" or "Move to Trash". For both of these options, resource will be removed from all the targets and XCode project file. However, if you choose "Move to Trash" it will also be removed from the folder in your hard disk.