The two terms data matching and deduplication are often used synonymously.
In the data quality world deduplication is used to describe a process where two or more data records, that describes the same real-world entity, are merged into one golden record. This can be executed in different ways as told in the post Three Master Data Survivorship Approaches.
Data matching can be seen as an overarching discipline to deduplication. Data matching is used to identify the duplicate candidates in deduplication. Data matching can also be used to identify matching data records between internal and external data sources as examined in the post Third-Party Data Enrichment in MDM and DQM.
As an end-user organization you can implement data matching / deduplication technology from either pure play Data Quality Management (DQM) solution providers or through data management suites and Master Data Management (MDM) solutions as reported in the post DQM Tools In and Around MDM Tools.
When matching internal data records against external sources one often used approach is utilizing the data matching capabilities at the third-party data provider. Such providers as Dun & Bradstreet (D&B), Experian and others offer this service in addition to offering the third-party data.
To close the circle, end-user organizations can use the external data matching result to improve the internal deduplication and more. One example is to apply a matched duns-numbers from D&B for company records as a strong deduplication candidate selection criterium. In addition, such data matching results may often result not in a deduplication, but in building hierarchies of master data.