Even though you have to start a new brewing cycle each time, pressurizing the water makes it run much quicker than a drip cycle. It's not as much pressure as you would find in an espresso machine, but enough to mean you can get a cup of coffee in less than a minute. An added bonus to the process is that some machines will actually produce a bit of foam on top similar to the crema on good espresso. The pressure system is usually louder when running than a passive drip coffee maker, so the machine can be a bit noisy when the brewing is underway. When it's not actually brewing, it's silent. So how do pod machines actually work? Rather than just heat the water, the machines have a boiler inside that rapidly heats the water and lets it build up pressure, which is then fired through the coffee grounds. But in order for the pressure and water flow to work right, you can't just scoop in some loose coffee grounds. You need the right kind of pre-packaged unit of coffee that fits in the machine, called a pod (hence the name "pod machines"). Each pod can only be used once, for one cup of coffee (or tea). Having to use pods is one of the drawbacks of the speedy pod machine, but buying pods is still cheaper than getting a cup of coffee at Starbucks. Some machines, like Senseo or Melitta's One:One, take a very generic style of pod that looks like a little round teabag filled with coffee. Not too fancy and easy to buy. They come in a variety of coffee styles and black or green tea. Other pod machines like Keurig or Tassimo are a bit more complicated, and they each only take their own kind of pods. Keurig has K-cups and Tassimo has T-discs.
In these cases, the pods are little plastic cups or capsules rather than flat gauze pads. The machines use the space in the cup as a little brewing chamber, which means a very flavorful cup. Both these machines make coffee and tea, and Tassimo even has hot chocolate. Pods can be bought with coffee from Green Mountain, Starbucks, Seattle's Best, Timothy's, and several other well-known coffee companies. Celestial Seasonings and Bigelow also make tea pods. So even though pod machines can limit your coffee choices somewhat, you will probably find that there are still more options than you could possible exhaust. Though they brew coffee, how pod machines work really makes them a lot more similar to espresso machines than to drip coffee makers.