Julia Child, in her book From Julia Child's Kitchen, defines seven stages of heating water. Other authors have given other definitions but most are similar to these.
1. Tepid: 85 to 105 degrees.
2. Warm: 115 to 120 degrees.
3. Hot: 130 to 135 degrees.
4. Poach: 180 to 190 degrees. This is the point at which the water starts to move. Julia Child calls this stage a "shiver" James Beard referred to it as "feeble ebullition." This is the stage to blanch at.
5. Simmer: 190 to 200 degrees. Bubbles start to show in the water. This is the point at which most stews are cooked and at which braising is done.
6. Slow boil: 205 degrees. There are slow rising bubbles forming.
7. The real boil, full boil or rolling boil: To heat a liquid to its boiling point (in the case of water this is 212° F) until bubbles break the surface. "Boil" also means to cook food in a boiling liquid.