On any given time period, you can place a box from a wick and span it across the chart. No interference of a price level usually means that outstanding orders still exist. Thus, buyers or sellers may be present at that level again to fight opposite of the trend since they were just pushing from those levels before.
It's a great gauge to understand how much price will struggle to pass through these distinct zones. For example, since Ethereum is bearish but found buyers at $89, $87, and $84, we can expect some support at these levels. The bigger the wick, the more it will struggle to pass through. This idea on its own does not indicate a bounce, especially because price failed to hold action above these levels. It just means it will fall less quickly in these areas, re-testing these same zones again.
I made the first level green because it should be the easiest zone to pass through; small wick, with small amount of buyers at that wick before price turned over again. The second level is yellow, because the wick is larger and had substantial buyers following that wick's action. The third level is red, because that wick is the largest in the series and had a very large amount of buyer's following it.