Invasive mechanical ventilation is part of the daily practice of the intensivist and anesthetist. The comprehensive knowledge of ventilatory modes is mandatory for managing the ventilated patients. The objective of this article is to explain the characteristics of the barometric and volumetric modes and the differences between controlled, assist-controlled, and assisted ventilation. The most common modes (volume and pressure assist-control, dual modes and pressure support) are described in detail. Parameters that must be set and those that must be monitored in each mode are also described. Finally, suggestions for initial settings are provided in order to offer the reader unfamiliar with mechanical ventilation a practical decision-making aid.