Slippage is the difference between the expected execution price and the actual execution price. It occurs during high volatility, low liquidity, or market gaps.
Positive slippage = better fill
Negative slippage = worse fill
You can reduce slippage by using limit orders, trading during high-liquidity sessions, and avoiding market orders during major news events. Even automated or stop orders may experience slippage in extreme conditions. This is a market characteristic rather than a platform-specific issue.