The giblets that come with a turkey are used to make turkey giblet gravy.
You usually cook the turkey giblets in with the gravy and it's supposed to give the gravy flavor.
You don't have to use the turkey giblet if you don't want too.
I personally do not like the turkey giblets added to gravy so I throw the turkey giblets out and only use the gravy.
The turkey neck is also used to cook in with the giblets and gravy and a lot of people do cook the turkey neck and giblets together but if you don't want too then you don't have too.
I just cook the turkey and then use the gravy without the turkey neck or giblets but it's up to you whether or not you want to use the turkey giblets or turkey neck along with the gravy.