Yeah, the terms are definitely confusing. Let me clarify.There...

Yeah, the terms are definitely confusing. Let me clarify.
There is one species, Cannabis sativa (cannabis). There are two broad categories of cannabis:
1. Plants grown for fibre, otherwise known as hemp. These plants are typically male, tall and thin with few branches.
2. Plants grown for cannabinoids, otherwise known as marijuana or 'drug-type'. These plants are typically female, are shorter and have more branches.
Female flowers produce much, much more cannabinoids per gram than male flowers as they are densely covered in trichomes, the organ in which cannabinoids are biosynthesized.

To meet regulations, hemp plants are bred to be super low in THC. Due to the genetic pathways that control the ratio of CBD and THC in the plant, hemp breeding results in plants that are high in CBD. However, due to their lack of branches and female flowers, they are not the most suitable for large scale CBD production.

Conversely, marijuana or drug-type plants have been bred to be very high in THC and therefore are typically very low in CBD. However, there are certain varieties of drug-type plants that do produce a high percentage of CBD, and since they are female with many branches and flowers, they are perfect for large scale CBD production.

Both CBD and THC, and many other of the 100+ cannabinoids found in the plant, have therapeutic aka medicinal properties. Hence any drug-type plant, regardless of whether it is high in THC or CBD can be considered as 'medicinal cannabis'. The term 'medicinal cannabis' is being used by the industry to try and differentiate the product from marijuana which typically has negative connotations for the wider public in countries like Australia. While a company could indeed extract CBD from a hemp plant, the overall yield would be significantly less than a female drug-type plant variety that has been bred to produce copious amounts of cannabinoids.
Hope that has helps clear up the confusion.