a MD/PhD teach degree, as the name implies, is a dual degree career obtaining both a MD and a PhD when you are done. THis degree is for people who want to be doctors and researchers at the same time. This is how it works.
You will apply to the program and get accepted to it. In your first 2 years you will start your PhD. Take the necessary coursework and pass your qualifying exam. The exam is the official starting point towards your PhD. You need to pass this exam in order to continue. After the first two years, you will then transfer to the medical school. For the next four years, you will work towards your medical degree. AFter those four years, you come back and finish your PhD, which usually takes an additional 3-4 years. Depending on the project. After your PhD, you will then be required to complete a fellowship for your MD.
All-in-all you are looking at 7-8 years of school. If you compare that to only medical school which is 4 years and grad school which is 5-6 years.
I see that you live in San Antonio, UTHSCSA has an amazing MD/PhD program who my previous mentor and supervisor runs. I highly reccomend you email him with any additional questions. His name is Jose Cavazos. Let him know that I send you and he will be more than glad to help.
Hope this information helps, good luck.