What is the difference between Facebook and LinkedIn ?

These two social media have completely different advertising system. The only similar thing is that both social media are created to attract traffic and of course they both analyse the demographic variables, location and profile information. The difference is the target audience, the cost of bid per click and so on so forth.

Marketers always choose where to promote their services and which social media will contribute to their marketing campaign. LinkedIn is created to those ones who are fond of lead generation and work in fintech services predominantly (at least according to my supervision). FB is for all niches and all business models.