Big Data refers to large, varied and complex sets of data that require specific technologies and tools to store, manage, analyze and exploit them. This data can be structured (for example, numerical data stored in databases) or unstructured (for example, textual data or multimedia files) and often comes from various sources such as sensors, social networks or online transactions. Big Data can be used to identify trends, patterns and relationships which can provide valuable information for decision making and innovation in many areas, such as business, science, health and safety.
Here is a more detailed article (in french) on the subject :