It's what people are saying online related to your topic. It's the “buzz” - the flow of ideas, forum threads, blog posts, comments, trends, news, links, catch-phrases, and other current content in your niche.
This ongoing “conversation” can tell you a lot about the needs and wants people have regarding your topic.
It can help you identify gaps in your niche that you can fill, trends you can capitalize on, products you can create, keywords you can target, places you can insert your content and links, and movers and shakers you'd like to work with.
You can't build a successful Authority Site in a vacuum. You have to keep your finger on the pulse of your niche!
Start immersing yourself in the conversation of your niche, and absorb the current buzz.