Poaching is nothing more than cooking a protein (often fish) by simmering it) in a liquid that has been infused with aromatics, or ingredients added to enhance flavor and aroma. This technique is used mostly successfully with proteins containing a high oil or fat content, such as salmon. Since the process doesn't call for fat, poaching is considered a healthy option for cooking proteins. 

Typically, a poaching liquid might be made up of water, wine, herbs, spices, and vegetables such as carrots, leeks or onions. Some cooks also include pungent flavors like fresh ginger, garlic or lemongrass. 

To poach, bring the liquid (water, wine or both) and aromatics to a simmer (190 degrees F), allowing the aromatics to bloom and flavors to develop. Season the item to be poached, gently lower it into the poaching liquid and cook it to the desired temperature.  Carefully remove it from the liquid, allowing any excess to fall off and then let it sit briefly to air dry before serving.