General liability is a business's legal liability to third parties that arises from its premises, its operations, and its products or completed work. The CDI outline describes commercial general liability as covering five forms of liability: premises, operations, products, completed operations and certain limited forms of contractual liability.
Exposures the CGL insures:
Premises and operations: a customer slips in the store; a worker's ladder falls on a passerby at a job site.
Products-completed operations: a product the business sold, or work it finished, later causes injury or damage.
Personal and advertising injury, such as libel in an ad.
Medical payments to injured members of the public, regardless of fault.
Exposures left for other policies:
Autos the insured owns or operates → commercial auto. Most aircraft and watercraft are excluded too.
Injury to the insured's own employees → workers' compensation and employers liability.
Professional errors → professional liability; employment practices → EPLI; most pollution → pollution liability.
Damage to the insured's own property → property insurance. That is first-party loss, not liability at all.