Can any doc tell me what's the difference between anorectal fistula and abscess?

Anal abscess/fistula: true perianal abscess arise from anal glands just up inside the anus. The gland gets blocked but pressure builds up and a tract is formed leading out from the gland to the perirectal spaces (anal fistula). An abscess forms . When the abscess is drained the tract (or fistula) dries up 50% of the time. In the other 50% it remains as an anal fistula, manifesting as a chroninc draining sinus .