Rectal hemorrhage refers to bleeding in the rectum. There are many causes of rectal hemorrhage, including hemorrhoids (which are dilated vessels in the perianal fat pads), rectal varices, proctitis (of various causes), stercal ulcers and infections. Diagnosis is usually made by proctoscopy, which is an endoscopic test.
Bleeding from the anus is termed anal hemorrhage and is usually superficial in nature.
References
Rectal hemorrhage Wikipedia(Text) CC BY-SA