The incontestable clause section in a life insurance policy states that after the life insurance policy is in force for two years, the insurance company cannot void the coverage because of misrepresentation or concealment by the insured person in obtaining the life insurance policy.
For example, when asked on the application if the you ever smoked, and you state "No", knowing that you have smoked for 20 years. Then, you die of lung cancer within 18 months of buying the life insurance, your insurance company may be able to contest the death benefit payment due to your material misrepresentation on the application, since you lied about the smoking, and you then passed away within 2 years from a health problem directly related to smoking.