Single-dose pods are small, usually plastic packages containing finely ground coffee that you place into a pod machine to create a fresh cup of coffee. As the water is heated up, it passes through the pod which is filled with coffee. The grounds are released through special holes in the bottom of the pod, allowing them to steep in the hot water.
Image Credit: http://nespresso.com
You can use pods in most types of pod machines, though they are designed for use primarily in Keurig or Nespresso machines. Capsules and cups made for Senseo and other traditional brewers will also work, but you need a special accessory machine.
When you're finished brewing, you simply remove the empty pods and place them into your recycling bin. It's that easy.