A basic drip coffee maker works by pulling water from the carafe reservoir in the back, boiling it and dripping it through a filter filled with coffee grounds. The grounds dissolve in the water and drain through to the pot, where the coffee stays heated until ready to drink.
The strength of the coffee depends on the ratio of coffee grounds to water. An ideal serving size begins with 2 tablespoons of coffee grounds per 6 ounces of water. More coffee grounds make a stronger, more bitter brew.
When the switch on a coffee maker is flicked, it opens the tube leading from the reservoir to the heating element, and the water flows down into it to be heated to boiling. After being heated to boiling, water's ability to act as a solvent increases and makes the coffee more quickly. The boiling water then travels up another tube and drips into the coffee filter, which is made of semi-permeable paper that admits liquid but not the solid coffee grounds. The coffee drips into the pot gradually. The heating element below the pot keeps the coffee warm.
Over time, deposits build up on the inside of the coffee pot from hard tap water. Failure to clean the pot negatively affects the taste of the coffee.