By extending a brand to more products, a business can make maximum use of the additional sales a strong brand can generate. Brand extension is most commonly done by adding products closely related to those already sold using a particular brand
Brand extension may be less obvious. A common example is adding products that appeal to the same market segment, exploiting the (presumably) good image a brand has in the minds of target customers.
Brand extension, if overdone, can risk diluting a brand. It may also make a business more dependent on that brand - and brands can weaken.