Hello, everyone. I searched in ENCODE for ChIP-Seq experiments and visualized them in UCSC browser. For instance, I searched for  [TATA-box binding protein (TBP) assays][1] and went to [FOS' promoter][2] to examine its TBP peaks. 

I kind-of get the idea of optimal Irreproducible Discovery Rate (IDR) for the peaks, but **I don't really understand the measure of "fold change over controls"** that UCSC gives you along the optimal IDR. Correct me if I'm wrong, but in the ChIP-Seq experiments' metadata (from ENCODE) it was stated that there was *no perturbation* (no treatment, no illness, nothing) in the samples, which makes me think those are the **controls**. If that's the case, then what exactly do they mean with "FC over controls", if the peaks are comming from "control" samples? 

  [1]: https://www.encodeproject.org/matrix/?type=Experiment&status=released&assay_slims=DNA%20binding&searchTerm=TBP
  [2]: http://genome.ucsc.edu/cgi-bin/hgTracks?db=hg38&lastVirtModeType=default&lastVirtModeExtraState=&virtModeType=default&virtMode=0&nonVirtPosition=&position=chr14%3A75278096-75280364
Control most likely represents the chromatin input control that the peaks were called against, so the background levels of the assay. 
If this is new to you I suggest you read about ChIP-seq and what kind of controls are commonly included.