A slot is a narrow opening that can be used for receiving or emitting signals. Slots are useful to prevent repeated delays in machinery, and they can be used to manage air traffic at airports.

Symbols on a slot machine represent a set of possible combinations that can earn credits based on the pay table. Typically, the pay table is listed on the machine’s face or in a help menu.

There are two types of slots: high and low. The high slot is the area in the middle of the ice above the face-off circles, while the low slot is directly in front of the goaltender. In hockey, the high slot is the prime spot to take a shot. It’s also the most accurate for wrist shots and allows a good view of the net.

Another type of slot is the expansion slot. These can include memory slots, PCI slots, AGP slots, and ISA slots.

If a signal is emitted connected to a slot, it is slower than if it was called directly. This means that you should not emit a signal to a slot that is not in the same class as the signal. You should only emit a signal to a slot if you’re sure that the signal will be compatible with that slot.

You can invoke slots by calling the signal-slot connection or by using the QObject::connect() method. Connecting signals to a slot is a much less expensive operation than contacting a receiver directly.