BPO is typically categorized into back office outsourcing - which includes internal business functions such as human resources or finance and accounting, and front office outsourcing - which includes customer-related services such as contact center services.
BPO that is contracted outside a company's country is called offshore outsourcing. BPO that is contracted to a company's neighboring (or nearby) country is called nearshore outsourcing.
Given the proximity of BPO to the information technology industry, it is also categorized as an information technology enabled service or ITES