What is the difference between ap and pa lateral chest xray.. which one shows the lungs as well?

Both, but...: Both show the lungs. The difference is the direction the x-rays pass through the body. Pa stands for posteroanteriorly (back to front) and ap stands for anteroposteriorly (front to back). If possible, pa is preferred because the heart shadow is smaller and lung fields appear bigger...But this is difficult for patients who are bedridden because the machine would have to be under the patient.