DD214 forms are military records of service. DD 214s are used to show your record of service time by breaking down your years of federal service. The Veteran's Administration (VA) uses this information to determine your benefits eligibility for programs such as VA home loans, retirement, unemployment, and education benefits such as the Montgomery GI Bill (MGIB) and the New GI Bill benefits. Often times, apartment complexes, universities, or car dealerships will offer deals to service members. They often ask for the DD-214 as proof of military service.
Our advice to you would be simply: don't lose your DD-214. However, if you do lose your DD-214, Veterans and service members can order new copies through the National Archives. You can learn more about the DD-214 and its history on Wikipedia's article about the DD-214.
There are several items not available through the National Archives, however. Find out what items you are responsible for keeping track of under all circumstances here.