Does anyone know why if I move a xcode project to another computer some files are broken?

I don't know how to correct but I need that when I move a xcode project to another computer, xcode don't recognize some files into the project and they will be red (but present in the folder). Can you help me?

Get Info on the files in question in the Groups & Files list, and ensure that Path Type is set to one of the relative values. Mostly likely the files that are showing as missing were set to Absolute.