What are collar stays, they are plastic/gold/stainless steel/brass things that go in the under side of your collar to keep that otherwise flabby piece of fabric stiff. Here are some great pieces of info from realmenrealstyle.com.
How to Use Collar Stays
Simply slide in the collar stay in the pocket on the underside of the dress shirt collar. After that, fold down the collar as normal. Remember that pointed shirt collars require pointed shirt stays. Rounded shirt collars call for rounded collar stays.
Also before you wash your dress shirt (or send the shirt to the dry cleaners), make sure you remove your collar stays. Also remove them before you iron your shirt. Collar stays are easy to lose can damage your dress shirt if left in by eithering tearing at the fabric during a wash or leaving a crease under an iron.
Remember its a man’s attention to detail that causes him to stand out and his style be noticed.