Most Active by Value lists equities by trade value. Multiply the stock price by the number of shares acquired or sold. It usually examines trading days.
Each stock is used to calculate this list. Multiply the traded shares by their price. This happens for every deal. From total value to lowest, they rate the stocks.
These stocks are usually very liquid. This means that a lot of people are buying and selling them. It also means that big institutions are involved. When you want to buy or sell a stock it is easier to do with these stocks. You can usually get a price.
Most Active by Value measures stock spending. Most Active by Volume only counts traded shares. It doesn't worry about share prices. Most Active by Value measures trading value, while Most Active by Volume measures share volume.