Order flow
The order book drawn over time, so you can see where large orders sat, moved and disappeared.
A liquidity heatmap, as in Bookmap or Jigsaw's Auction Vista, draws the order book across time behind the price. Each price is coloured by how much is resting there: brighter means more. Executed trades are drawn over it as dots or bubbles sized by volume.
A bright horizontal band is a 'wall' of resting orders. Watching it lets you see whether a wall holds when price arrives, gets eaten through, or is pulled just before price reaches it.
It needs full order book data from an exchange, so it works on futures and crypto, not spot forex.
For education only, not financial advice.