Free ads or free advertising means the publishing of your business on the free business listing websites or on the link submission websites.
At free business listing company, you may submit business without any charge. It will give benefit to all in multiple ways.
Business publisher, even if do not have any website, that may also publish and find presence of their business on google.
Being having presence of business on google gives free business promotion. Hence we can say free business submission to free listing portals gives benefit to publisher, website or portal and also the end user.