Are you referring to the Value High and Value Low of the day? See
VAH and
VAL.
Both of these are Market Profile terms, and to be honest to understand them it would be a great idea to read some of the introductory posts you will find here at the
Market Profile forum. Very educational indeed and well worth the time spent.
In brief, the value high and low are plotted around a central price referred to as the Point of Control (POC), which is the price that traded most frequently during the day according to time at price. The
POC is the longest line of TPOs on the Market Profile chart. The
VAH and
VAL are plotted so as to contain 70%, or thereabouts, of the day's trading, again as measured in number of TPOs.