Serratus — The serratus muscles are the muscles the side of your upper body, above your obliques and by the side of your pecs between the pecs and lats. They provide support when you carry things and help keep carried items away from the motion path of the thighs. When large and developed, they look like wings on your back.
Standing heel raises with or without dumbbells is an example.
They look like ribs but are more pronounced and obviously made up of muscle. Furthermore, having uneven hamstrings and quads can lead to a variety of problems in your knees and lower spine by pulling on them unevenly.
Lats The "lats" are the latissimus dorsithe somewhat large muscles of the upper back on the outside below the armpit. Chest Chest exercises like push ups, bench press, and dips will build a great chest.
They are useful for downwards pushing or upward straightening movements pivoting at the elbows. The back is a HUGE major muscle group; one of the biggest muscle groups in your body.
They are key muscles when you lift your heels up, such as when you walk, run, and go upstairs. Rhomboids are underneath your traps but very important as they hold the scapula onto the ribcage and help retract the scapula.