Ventral means the front of your body, as opposed to hiatal (stomach), inguinal (inguinal canal), umbilical (belly button), etc. A hernia is when part of your insides (intestines) protrude (stick out) through a muscle or between muscles where they are not meant to.
"When muscle or connective tissue (fascia) becomes weak, a hole is created, and an organ or fatty tissue can squeeze through it. Hernias are common." (copied from somewhere as it is well put.
It is not uncommon after a surgery for the muscles that were cut to not be as strong as they are along the incision, and for them to separate a little, letting your guts bulge through a little.
An "incarcerated" hernia means it can not be gently pushed back into place, back through the opening to where it belongs. This can cause stuff insides the intestine to not proceed on like it should, but just sit there. Blood supply can be cut off, leading to a serious condition (strangulated hernia) which is an emergency condition (surgery now before part of your intestine dies, breaks, etc). THIS IS RARE, but something that is always watched for with hernias.
http://www.wisegeek.com/what-is-an-incarcerated-hernia.htm"In a reducible hernia, herniated material can move freely in and out of the hernial sack. This can cause pain and assorted complications, but it is not an immediate threat. Incarcerated hernias, on the other hand, involve tissue which becomes trapped, which means that the blood supply could potentially be cut off as the herniated material is squeezed. In the case of hernias involving the intestines, the intestines can become obstructed in an incarcerated hernia, causing nausea, vomiting, and other digestive problems."
Symptoms to watch for are nausea and vomiting, severe pain or changing levels of pain (may come and go), if you notice the hernia is harder/firmer, bowel movement pattern is not like it usually is (if you quit pooping). If these happen, get help.
Again, hernias are very common and just watch yourself. I imagine your doc told you to not strain on the toilet and to avoid lifting heavy things (both of which increase pressure inside your abdomen). They are finding different ways to repair them, using different mesh for your body to incorporate in its tissues to prevent the weakened area from opening up again.