It sounds like it's gonna be a mint or stick of gum, but it's more like an exercise. There are different techniques, but all are about paying attention to that silly little thing you do all day in and out of your nose.
When I started yoga I thought the breathing techniques (known in Sanskrit as Pranayama) were a load of crap, and you may think so too. But consider, the diaphragm (your primary breathing muscle) can be purposely controlled (like a bicep), or it can run automatically (like the muscles of your esophagus). I can't think of another muscle that you can control with your conscious AND subconscious mind. Anyway, controlled breathing has brought me a lot of relief from anxiety and I recommend you try it while meditating or riding the subway during rush hour! It's all good. Note: pregnant women should never hold their breath during pranayama.
Our animated You Tube friend is ironic and informative at the same time: