After an insurance policy is issued to you, you have a certain period of time (usually 30 days) during which you can change your mind and cancel the policy for any reason whatsoever. This is often called a "free-look period." If you cancel your policy during the free-look period, your premiums will be refunded in full, and no claims will be paid. (This type of cancellation is treated as though your policy never took effect.)
A fixed number of days, generally 10, during which you may cancel an annuity contract such as Vanguard's Variable Annuity Plan.
A period during which the applicant has the right to examine the insurance policy/certificate (generally within 10-30 days after the date of receipt) and to cancel the coverage if not satisfied for any reason. Any premium paid during that period is returned and the coverage is considered never to have been in effect.