Pods are tea-bag-like, single-serving-sized paper sacks of ground, blended espresso intended to fit into special filters provided with many pump espresso machines. They are typically packaged in single-serving foil envelopes. You open the envelope, pop the pod into the filter, and brew. The pod comes out of the filter as cleanly and simply as it went in.
Pods offer clear reassurance for the beginner because they are easy to use and guarantee a proper dose of properly ground coffee. However, they are very expensive, offer limited choice of coffee, and can only be used with pod-compatible pump machines. Furthermore, they create a good deal more waste packaging than whole-bean coffees.
Some pods are proprietary in format and designed to work with only one brand of machine, and visa-versa. Increasingly, however, home pump machines are designed to give users the option of using either regular ground coffee or generic pods that work with any machine that follows something called the ESE (Easing Serving Espresso) standard.
Nespresso Pods, Nespresso