2.78 Understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis

Homeostasis is the control of internal conditions basically. Examples of this include:

• Osmoregulation: control of water
• Thermoregulation: control of temperature

Thermoregulation is essential because (at least for humans), 37°C is about the optimum temperature for your body to function. Osmoregulation is also important so that the plasma in the blood isn't too dilute and isn't too concentrated (more on that in urinary system posts)

Here's a random GIF because why not