Rollover
Rollover is the carrying of a position from one settlement day to the next, or from one futures expiry to the next.
In retail forex, no currency is ever delivered: every evening, the broker rolls your position to the next day. That mechanism is what generates the swap. Rollover time, around midnight platform time, often coincides with a temporary widening of spreads.
On futures and futures-based CFDs (oil, gas, sometimes indices), rollover means switching from one expiry to the next. The displayed price can then jump, and the broker applies an adjustment to neutralise the gap.
Avoid placing tight orders right around that time: wider spreads can trigger a stop without any real market move.
See also