This means that if you want to integrate your system with other systems, like your website or accountingdatabase or if you want to perform complex customizations (and have the expertise to do so) you can dig into the entrails of SugarCRM to make it do exactly what you want it to do.
This may mean that you use low-cost Web-based services to provide order taking, accounting, e-mail services, database management, or a hundred other functions that are central to the operation of your business.