A spot trader is a type of prop trader who buys and sells securities, commodities, or currencies with the intent of holding the position for a short period of time. Spot traders generally don't have a bias towards any particular direction in the market; they simply attempt to take advantage of short-term imbalances in supply and demand.
Because they hold their positions for such a short period of time, spot traders typically don't take into account broad fundamental factors when making their trading decisions. Instead, they focus on things like price momentum and technical indicators.