Term life insurance is issued to individuals and owned by the individual insured, or the owner of the policy who pays the premium. With term life insurance you are insured for a set number of years, usually from 10 to 30 years. If you leave your job, you still have the insurance.
With Group term life insurance you are not the owner of the policy, it is a group policy issued on behalf of your employer to cover the employees listed as members of the group plan.
The group coverage is usually annual renewable coverage, and if you are no longer employed by the employer, then you no longer have coverage under the group plan.
Learn more about term life versus group term life insurance coverage.