Key Concepts
Trading successfully requires understanding the basic mechanics of an exchange. Below are the core terms you will see across prediction platforms like Kalshi and Polymarket.
Bids, Asks, and Spreads
When you navigate a market interface, you are interacting with two core pricing points:
- The Bid: The highest price any trader is currently offering to buy a share.
- The Ask: The lowest price any trader is currently offering to sell a share.
The difference between these two figures is called the Spread.
Why Spreads Matter
The spread represents the implicit cost of trading immediately. If the bid is $0.50 and the ask is $0.52, buying instantly costs you $0.52, but you could only sell it back in the identical instant for $0.50. Tighter spreads (e.g., $0.50 vs $0.51) indicate a highly liquid market that is cheaper to navigate.
Liquidity and Slippage
Liquidity describes how easily you can enter or exit a position without moving the market too much.
- High Liquidity: Markets with deep order books and tighter spreads.
- Low Liquidity: Niche markets where even modest orders can shift the price.
Slippage is the difference between the expected price of a trade when you hit the 'Buy' button and the price at which the trade actually executes. In low liquidity environments, purchasing 1,000 shares might require sweeping multiple price levels in the order book, dragging your average purchase price significantly higher than what you initially visualized.
Types of Orders
When using an order-book platform, order type affects both speed and execution quality.
- Market Order: Executes immediately at the best currently available price in the order book. This prioritizes speed over price efficiency, which can make it vulnerable to slippage.
- Limit Order: You specify the highest price you are willing to pay, or the lowest price you are willing to accept. The order rests in the book until another trader matches it. This gives you more price control, but your trade may never execute.