The DICOM image is same as an MP3 file as the mp3 file consists of background data like Album,artist,composer,...etc.. in the same way a dicom image also consists the data about the image like name of the patient, age, no. of frames, ... etc but for each item in the meta data there will be a an ID .
for example for the patient name the Id is (0010,0010) .
the Dicom image can be converted in to any image format like BMP,TIFF,JPEG,....
you can download a DICOM viewer here
Hope this helps you..