Commercial General Liability is the foundational business policy. It responds when someone who isn't an employee is physically injured or has property damaged in connection with your business — a visitor injured at your office, damage caused at a customer site, an injury at an event you hosted. It also covers personal and advertising injury: libel, slander, and certain advertising-related offenses.
For a software company, GL is rarely the policy that pays a real claim. It is, however, the policy every landlord, conference venue, and customer procurement team requires evidence of, almost always at $1M per occurrence and $2M aggregate. It is inexpensive and it unblocks contracts, which is reason enough.
Most technology companies buy GL as part of a Business Owner's Policy alongside commercial property, which is both cheaper and simpler to administer than separate policies.