I also think you probably mean "DO" rather than "OD", but I'll give a brief summary of what I know about the degrees.
OD - "Optometry Doctor" (I believe). Limited to writing eyeglass prescriptions and able to prescribe some eye medications for common conditions like glaucoma. It is my understanding that Optometrists are not allowed to do surgery in most states, though I have heard that in some places (New Mexico?) this may be changing.
Sorry if this part is long:
DO - "Doctor of Osteopathy". There's actually a long history to this field, dating back to the 1800s. My understanding is that originally it was intended to be more scientific than MDs, who at that time had a lot of quacks in the field. With the increasing standardization of medical education, MDs became the dominant field, and DOs tended to be more "holistic", focusing on the use of manipulation (think chiropractor techniques, but more varied and using more of the body than just the spine).
A generation or two ago, MDs looked down on DOs, believing that they received a substandard education and were not as grounded in science as MDs. There may have been some truth to this back then. However, over the last few decades, DO schools have adopted a curriculum that is essentially identical to MD schools (with the caveat that they continue to teach "manipulation" techniques to treat a variety of conditions). Today, there is essentially no difference between MDs and DOs. Both are considered fully-licensed physicians, and can become trained in any specialty. There are MDs and DOs in every field from Internal Medicine to Neurosurgery.
That being said, you will still find pockets of prejudice in both the DO and MD community. Some DOs claim that they are more "patient-oriented" and "holistic" than MDs. Some MDs argue that, because the average academic qualifications of students who get into DO school are lower than MD students, they are essentially "MD-rejects".
Personally (I'm an MD), I have worked with and trained under both MDs and DOs, and I don't see any fundamental differences, other than the letters on their lab coats.