Spread is a difference between bid and ask price. It works the same way as exchange rates in bank.
The lower the spread is the better for traders.
It's also one way how brokers earn on clients' trades. No matter if they are winning or losing.
Brokers offering lowest spread - already from 0pips - usually count you some fees for every trade which are commissions. Again as spread no matter if the trade is winning or losing.
Some broker charge traders with both spread (usually lower one) and comissions