The difference between identical and fraternal twins is Identical twins occur from a single fertilized egg while fraternal twins come from two different fertilized eggs.
More Info: In some cases, identical twins may even share the same yolk sac. Fraternal twins do not exhibit this rare trait and development doesn't coincide in an almost identical manner. Even before birth, identical twins will typically develop and mature within the same timeframes, a phenomenon that usually continues throughout the rest of their lives.
Contrary to popular belief, fraternal twins can also look very similar and vice versa. However, the main difference between identical and fraternal twins lies in their DNA. The DNA of identical twins is rarely ever exact but differences are usually quite small. In fraternal twins, there are typically significant differences in genetic makeup that are found among other types of siblings.
Relationships between twins may also frequently differ. Identical twins may share more in common than fraternal twins when it comes to personality, interests, learning, and many other factors. Whether or not this is based on biological factors or nurturing of the identical twins is a widely debated topic. In some instances, these behaviors have been noted in fraternal twins, some that were discovered in fact to be identical twins.