Outsourcing refers to outsourcing business activities traditionally handled internally to external providers. Companies outsource to reduce costs, access new skills and technologies, and focus on core competencies. Common business functions that are outsourced include IT services, customer support, accounting and human resources. A company must evaluate which activities are core to their strategy and competitiveness before deciding to outsource. Effective outsourcing requires proper planning, vendor selection and ongoing management through a service level agreement.