This involves the collection of data as an evaluation basis for the strategic orientation and control of marketing actions or campaigns.
Knowing your customers as precisely as possible has always been a key to successful marketing. This is more relevant today than ever before - more and more companies are recognising this - and are using it to advertise with better performance than others (read more about this in the IBM study, for example).
A tool for collecting data is e.g. Google Analytics for the web.