Basically, we know that advertising depends upon how effectively you can reach the customer. Online advertising, the rapidly popular and widespread form of promotional activity, is used by these small and large firms to target customers.
This target area is set according to the base of operations of the business. For example, a grocery store would be using a simple Geo fence that covers the local residents, while multinational would use a complex fence, including all countries that it operates in. This helps in keeping the marketing effort relevant. Another example would be of retailers selling a specific product, who would look at the area from where most of their customers come from, and shift their base there.
In order to get a higher quality and quantity of customers, companies can use this method to easily select the scope of their search: country, state, city, DMA, metro, or zip code. They can even set up a custom radius for the fence.