What does the Data Companies actually do??

[Thersibley]

There are companies who provide insight and data about the audience to the marketing companies. So, they can target the audience more carefully and have conversions. But exactly do they do? I mean Facebook also gathers data, how this is different from theirs?
Well, some of these insights come from platforms built by specialists. A fintech app development firm might create tools that integrate and analyze multi-source data, offering marketers a wider view than just one platform, like Facebook.