The first DD Form 214s were issued in 1950, after replacing the older "WD AGO" (War Department Adjutant General's Office) Forms and the NAVPERS (Naval Personnel) discharge documents. The latter had been in use since 1941.
Often, a veteran is asked for a DD Form 214 when, because they served before 1950, their discharge is one of the other documents listed above.
Individuals that served in the Air National Guard or Army National Guard, and did not serve any active duty time (ie: activation under Title 10), will receive an NGB-22 from the National Guard, not a DD Form 214.
A military discharge (DD Form 214 etc.) is required to apply for most VA benefits, to verify military service for a job application, to verify service for membership in a service organization and many other reasons.
If you don't have your discharge, a Request Pertaining to Military Records should be submitted to the National Personnel Records Center using a Standard Form 180. Contact the VSA for the form or go to www.archives.gov/veterans/military-service-records/ .
Additionally, the National Personnel Records Center stores veteran's medical and service records which can also be requested using the Standard Form 180.