I wonder what influencer marketing is.
It's a type of marketing that's focused on individuals. You see it in social media. 
Who well know infuencer should I know?
The Kardashians might be an example. Their tastes influence certain potential buyers.
What products do they promote?
Different diet, fashion, and cosmetics. Influencers sometimes basically give testimonials to how much they like a product, and that makes others want to buy it. 
Ok but they disclose that they are paid to do that or are they sneaky about it.?
Usually more sneaky about it. Other "value-added" influencers might be journalists or industry analysts.  If they say a product is good, people believe them.
Hmm yes I guess is someone I likes recommend a product I will sure check it but I would like to know if they are been paid or not.
This does way back to "two step flow of communication" -- a concept from 1940.