This is a question that a lot of people ask so don’t feel stupid for not knowing the answer. Now as a product there is very little difference between cannabis and marijuana. The main difference is hidden within the meaning of the words. The difference between the words is similar to that of saying wheels instead of car or saying axe instead of guitar however it may be a little less likely to get you beaten up by anyone who happens to overhear you saying it.
The basic difference is this; cannabis is the scientific name, the real name of the plant. The word marijuana is of Mexican origin, coming from the word marihuana, and is merely a nickname that has spread across the world.
Now this is technically the only actual difference but I think there are quite a few other little differences between the words. By this I mean how they are received by society. Cannabis, as the official name, has always sounded a little more proper. To the average mind cannabis is associated with the word medicinal. I believe that this is partly because of the types of people that you would come across using the word cannabis or the word marijuana. Cannabis, as a term, is more likely to be used by doctors, botanists or what have you however marijuana, as a nickname, is more casual and conjures images of stoned teenagers.
This difference in the words alone show that even though the words refer to the same item it is possible to see a difference in product from the just a name. Cannabis is grown in seed banks for official legal use and marijuana is grown in basements and back gardens. The same product receiving a different title which is completely dependent on the circumstances under which it is cultivated.
A few people would argue that quality is also a defining trait when pondering the slight differences between cannabis and marijuana. Cannabis, because of its official stature, could be argued to be of a higher quality than marijuana. This completely assumes that my previous statement concerning labs and gardens is true. So perhaps cannabis of a higher quality would be called cannabis and that of a lower quality or of a dodgy background could be called marijuana.
All of this is purely subjective; the only thing that is completely certain is the original statement. Cannabis is the scientific and official name of the plant whereas marijuana is just a catchy nickname.