Sous vide is a technique in which food, usually sealed in a suitable bag, cooks in a closely controlled water bath or steam environment. An immersion circulator maintains the bath temperature. Browning often requires a separate searing step.
Temperature alone does not determine food safety: thickness, cooking time, handling and cooling also matter. Follow a validated time-and-temperature method. A vacuum bag does not preserve raw or cooked food indefinitely, and sous vide is more specific than the broader term precision cooking.
Reference: Further reading.