A shirt with one pocket usually located at the left chest of a man. This type of shirt usually used for some utility purposes like you has to put something in there.
A Dress Shirt With Two Pockets
A chest pocket on both sides is very casual and usually reserved for very informal purposes.
A Dress Shirt Without Pockets
Some men like to have a shirt pocket but others don’t. Technically, a shirt with a pocket was less formal than one without. This kind of shirt also set as an informal fashion. If you’re looking for a more formal dress shirt, a shirt without pockets is the best option for you. No visible chest pockets show a more sophisticated fashion than others which has.