The potential of Big Data for sociology is being recognized broadly, but there is still a wide gap between its potential and its realization. One of the reasons is that Big Data encloses types of data which are very different. This articles aims to identify the features of Big Data that are common to other traditional sociological data such as registers, traces and documents. Secondly, its purpose is to propose a typology of Big Data based on four criteria: data origin, flexibility, presence of operational definitions, presence of metadata. Finally, the main methodological issues deriving from the different phases of the data production process are presented for every type of Big Data.