In the recent redesign we removed the evidence pyramids in the results panel, after some feedback we have just reinstated them:

The evidence pyramid concept is explained in this diagram and accompanying text:

Evidence pyramids are not perfect, for instance a poor systematic review is no match for a good RCT. But our evidence pyramids are useful in attempting to convey the potential level of evidence for each result. We use 5 levels in our simplified pyramid and they are colour coded to match the narrative description of the record (e.g ‘systematic review’ is green or ‘key primary research’ is dark blue) and that corresponds to the same colour in the filter results column:

In short, these are a simply tool to help convey the potential robustness of the evidence.