Both of the above are correct. To clarify, adhesions are bands of scar tissue that form internally in response to surgery, trauma, infection, foreign bodies, etc. When viewed directly, they appear almost like ligaments or tendons, in that they are dense tissue that do not stretch.
Anyone who has had abdominal surgery has adhesions. Most of the time they feel like nothing because they do not have nerves in them, unless nerves got trapped in them incidentally. They do not show up on x-rays or other imaging, other than by what effect they may have on other structures or organs.
Adhesions feel like nothing to most people because they don't cause problems for the most part. But, when they do cause problems (for us in particular), it is generally in the form of small bowel obstruction, either partial or complete. So, if you look that up, then that is what it feels like. Some people who have chronic partial obstruction or nerves entrapped by adhesions will have chronic abdominal pain that is unexplained by ruling out other causes.
Treatment is either living with it or having them surgically released (lysis of adhesions). Most surgeons will avoid this, because more surgery can cause more adhesions, even if they use an adhesion barrier product (but those products do reduce the risk for most people). Some people state that they get good relief from deep tissue massage to break up adhesions, but I am not sure how safe it is or if tearing adhesions will cause new adhesions to form from the trauma and/or bleeding.
Hope that explains it enough for you.
Jan