Spread is a difference between the buy price (ask) and the sell price (bid) of a trading instrument.
The smaller the spread, the earlier you can enter the profit zone of an open position. That's why many people focus on spreads as a major part of the trading costs for active trading.
Each instrument has a minimum spread - the smallest value of the floating spread, expressed in pips/points; and a typical spread - the typical value of the floating spread under normal market conditions.