Encyclopædia Britannica defines data mining as “knowledge discovery [through] the process of discovering interesting and useful patterns and relationships in large volumes of data. The field combines tools from statistics and artificial intelligence with database management to analyse large digital collections, known as data sets.” Or put slightly differently, the term describes the process of extracting insights and knowledge from large data sets, that is the processing of information, e.g. available and extracted (mined) from social media platforms.
We will soon provide you with more on this topic, but until then, check out this introductory article by Chen et al. (1996). Also, check out the SIGKDD, the Association for Computing Machinery’s Special Interest Group on Knowledge Discovery and Data Mining, and its publications on data mining.