Poaching is cooking over steam rising from boiling water in the bottom of a cookware like a pan. Egg poacher or boiler is a covered pan containing a steel plate, egg holder with depressions or shallow cups in each of which an egg can be cooked over steam rising from simmering or boiling water in the bottom of the pan; OR a kitchen tool that enables eggs to be easily cooked when poaching is desired. There are a variety of different utensils for this purpose, such as individual metal cups, groups of connected cups, poaching spoons, microwavable poaching cups, poaching pans with poaching cups, and electric egg poachers; or a baking dish in which food such as eggs, fish, potatoes, tomatoes, etc. can be poached.
The perfect poached egg has a runny yolk, with a hardening crust and no raw white remaining. In countries that mandate universal salmonella vaccination for hens, eating eggs with a runny yolk is perfectly safe. You can as well poach for a bit longer for a soft non-runny yolk or even longer for a hard yolk.