An SR-22 is not insurance, but rather a form filed by your insurance company stating that you have purchased auto liability insurance. (Liability insurance pays for property damage or bodily injury caused by the insured in the event of an accident.)
In most cases, SR22s are required if you have gotten a DUI or DWI, have been at fault in an accident and were uninsured, have received too many tickets in a short period of time or have had your license suspended or revoked.
SR22 requisites vary from state to state and some states—Delaware, Kentucky, Minnesota, New Mexico, Oklahoma and Pennsylvania—don't require them at all. However, if you have an SR22 in one state and move to one of the aforementioned states, you must continue to meet the filing and liability limit requirements of your former state.
Because most offenses that require an SR22 also hike up auto insurance rates, it's an ideal time to shop for insurance to ensure you are paying the lowest price.