ForexECN vs market maker brokers
Brokers fill your orders in different ways. Some pass them to outside liquidity providers; others take the other side themselves. Both models are legal and common. What matters is how the broker manages the conflict and what it costs you.
The main models
Market maker (dealing desk). The broker quotes its own prices and is the counterparty to your trades. Spreads are often fixed or wider and commission-free.
STP (straight-through processing). Orders are passed to one or more liquidity providers, usually with a mark-up added to the spread.
ECN. Orders meet prices from several liquidity providers. Raw spreads are tight and the broker charges a commission per lot.
Many brokers mix models, keeping some client trades in-house and passing others on. Account names such as "ECN" or "Raw" describe pricing, not always how orders are routed.
What to check in the documents
Read the order execution policy and the conflicts of interest policy. Regulated brokers in the UK and EU must publish both. Look for how prices are formed, whether slippage can go in your favour as well as against you, and what the broker does in fast markets.