Commission
Commission is a fixed fee your broker charges on each order, on top of the spread. It is mostly found on ECN or raw spread accounts.
On raw spread accounts, the broker earns mainly through commission, quoted per lot and per side or round turn. On shares, it is often a percentage of the trade value or a minimum per order.
To compare, convert everything into pips. On EUR/USD, one pip is worth about $10 per lot, so a $7 round-turn commission equals 0.7 pip, to be added to the spread.
For a scalper making many trades a day, commission becomes a major expense. For a swing trader, it matters less than the spread during news and the swap.
See also