What is exactly is an anal abscess/fistula?

An infection. In the perianal region, usually derived from the anal glands inside the rectum. A fistula is an abnormal communication between two organs, in this case the rectum and the skin outside the anus. Both require evaluation and often surgery to permanently resolve and prevent recurrences or complications.
Anal Abscess. An anal abscess is a painful condition in which a collection of pus develops near the anus. Most anal abscesses are a result of infection from small anal glands. http://www.webmd.com/a-to-z-guides/anal-abscess.
An infection/tear . An anal fistula is an abnormal connection between the anus and something else, such as the skin or bladder. This is called an abscess if an infection develops. An abscess can occur without a fistula.

Related Questions

What are common symptoms of an anal abscess/fistula?

Pain . Anal abscess or fistula typically cause pain near the rectum. The fistulae moreso during bowel movements. Both are important to diagnose and treat, especially an abscess as this can cause death or disability if not treated promptly. Read more...
Pain, Swelling and drainage of purulent material/fluid, maybe fever. Proper drainage and possible surgical correction of the fistula is necessary. Read more...
Butt pain . A persistent 'pain in the butt' should be eval by a doctor or at least have your butt look at under the light of day. Read more...
Anal Abscess. An anal abscess is a painful condition in which a collection of pus develops near the anus. Most anal abscesses are a result of infection from small anal glands. http://www.webmd.com/a-to-z-guides/anal-abscess. Read more...

Could a hard fall cause an anorectal abscess and anal fistula?

Yes. Trauma is a known and common cause of infections resulting in abscess and fistula. Consult with a surgeon for further evaluation. Read more...

Is it possible for a hard fall to cause both an anorectal abscess and an anal fistula?

Unusual. Trauma to the rectum may result in injury that would cause swelling and posinly a hematoma (blood clot) and this might become infected. In abscess would usually be the result of a penetrating injury. Read more...

Could you tell me if this consistently draining anal abscess isn't painful could it still be a fistula?

Yes. You need an exam by a surgeon. Sometimes you may need an exam under anesthesia to correctly diagnose it and treat it at the same time. It could very well be an abscess which hasnt been treated properly. Read more...