Why you should know this
The top price may cover only a small quantity; depth shows how an order may move through several levels.
This is not about being told which trade to take. We are learning how to inspect the mechanism together, so a later decision is more deliberate and reviewable.
The short answer
This lesson introduces bids, asks, levels and visible liquidity without treating them as guaranteed.
What an order book contains
A central limit order book records eligible resting buy and sell orders for one pair on one venue.
The bid side usually lists buyers, with the highest price closest to the middle. The ask side lists sellers, with the lowest price closest to the middle.
A simplified fictional Token A/PHP book might look like this:
| Asks | Quantity |
|---|---|
| ₱103 | 300 |
| ₱102 | 200 |
| ₱101 | 100 |
| Bids | Quantity |
|---|---|
| ₱100 | 150 |
| ₱99 | 250 |
| ₱98 | 500 |
The best ask is ₱101. The best bid is ₱100. The spread is ₱1.
Cumulative depth
Cumulative depth adds quantities from the best price outward.
On the ask side above:
- up to ₱101: 100 units;
- up to ₱102: 300 units total;
- up to ₱103: 600 units total.
A market buy for 450 units could take:
- 100 at ₱101;
- 200 at ₱102;
- 150 at ₱103.
Its quote cost is:
(100 × 101) + (200 × 102) + (150 × 103) = ₱45,950
Average fill:
₱45,950 ÷ 450 = ₱102.11 approximately.
The best ask was ₱101, but only the first 100 units were offered there.
Depth chart: useful summary, not prophecy
A depth chart turns cumulative bids and asks into two curves. It can quickly show where visible quantity is concentrated.
But the chart is a snapshot. Orders can be added, cancelled, filled or moved. A large “wall” may disappear before price reaches it. Other liquidity may appear only when the market moves.
Use depth to estimate current conditions, not to declare that price cannot cross a wall.
Displayed liquidity can vanish
Displayed orders are not deposits locked for our personal use. Until matched, eligible orders may often be cancelled or changed. During fast news, several levels can disappear before a market order arrives.
Therefore an average-fill estimate is a scenario, not a guarantee. The larger our size and the faster the market, the less confidence we should place in a static screenshot.
Hidden, reserve and off-book liquidity
Some markets may support hidden or reserve instructions, while brokers and OTC desks can hold liquidity outside the public book. Not every participant or available transaction appears in the visible rows.
The opposite is also true: visible size may not remain. Order-book reading is valuable precisely because it is incomplete but actionable information—not complete truth.
A familiar Philippine or Asian example
A learner in the Philippines studies a fictional crypto quote and writes the pair direction, intended action, price control, estimated cost, possible fill problem and exit plan. The exercise uses paper values only. No order is placed.
One risk or limitation
Examples simplify execution. Real venues differ in order logic, trigger source, fees, tick and lot sizes, available liquidity and outage handling. A checklist can reduce avoidable mistakes, but it cannot guarantee a price, fill, exit or profit.
How this connects to market mastery
Market mastery includes execution discipline. A strong market view can still fail when the pair, order type, size, liquidity, fee or exit mechanics are misunderstood.
Quick check — no money needed
Use a fictional quote. Write the pair, buy or sell action, order type, price control, size, estimated fees, liquidity concern and the condition that would cancel the plan. Then explain which field protects you from the largest avoidable mistake.
If you can explain your answer and name the main limitation, this lesson is complete.
*Cryptocurrency and virtual asset transactions are highly volatile and irreversible, may result in significant losses, and do not guarantee returns; customers should trade only after understanding the risks involved.
