Answer:
Blanching vegetables involves immersing them in boiling, usually salted, water for a short period of time, and then draining. Blanching is appropriate for vegetables that require very little cooking or could even be eaten raw: green beans, asparagus, etc.
For green vegetables, blanching is usually followed immediately by an ice bath; as rapid cooling is needed to stop cooking and preserve the green colour (which breaks down after about 7 minutes of cooking).