Call centers and BPO are both very similar. A call center is an established area where employees manage incoming and outgoing calls. These can be anything from outbound telemarketing, survey generation, incoming customer support, etc. Basically a business uses a call center to streamline any subset of it’s phone operations. This may also include order taking.
BPO, or Business Process Outsourcing, generally means that the business is from a different country or location. While BPO can certainly consist of call centers, it can encompass many different business functions such as transcriptions, record maintenance, or accounting.
A Business Process Outsourcing company generally partners with another company to manage one or more aspects of that companies business. Most companies that use outsourcing as part of their strategy do so to save costs. It is often times much more efficient to hire a third party organization over seas than to build and hire locally.
A call center can certainly be thought of as a BPO organization, however, their scope and involvement with the hiring company is simple telephone related.
So Lets recap:
Call Center - A BPO organization that handles telephone operations for another company. These operations may include incoming customer support, outgoing telemarketing, survey generation, client relations, etc.
BPO - Business Process Organization. This type of company, while similar to a call center, takes on more general tasks. These may include medical record storage, accounting, or software development.