This is mentioned because in certain countries there are some well-respected or common alternative medicines that are not categorized under EBM. The term ‘alternative’ is used because these medicines or remedies are often disproven, unproven, or difficult or impossible to prove by the standards used in and required by evidence based medicine. For instance, in many English-based journals established in countries including the UK and US, hard science is king, where EBM studies give figures and burdens of proof. They tend to specify all quantifiable data such as the target population, treatment intervention, outcomes, and methods to test specific hypotheses, and often use double-blind clinical trials (Reference: https://en.wikipedia.org/wiki/Evidence-based_medicine).
An example of CAM is Traditional Chinese Medicine (TCM). Even though it was once the mainstream practice (hence why it is called Traditional Chinese Medicine), in our modern society you will most likely find that TCM is under the label of CAM because often TCM studies cannot provide as rigorous standards of proof. The bias is then how can a researcher in TCM hope to publish in mainstream medical journals? Consequently, such studies tend to be published in TCM specific journals, rather than mainstream EBM journals and be compared to other studies with the same basis.
If you are referring to or writing on this topic, attention should be paid to how different standards of proof are used otherwise it would be deemed ignorant. In EBM for instance, if the author is conducting test in their respective country they need to adhere to that country’s’ respective guidelines and policies (i.e. the permitted daily dosage of a particular drug may differ from country to country), at the same time when analyzing and presenting the results, be aware of the grading systems for assessing the quality of evidence (i.e. the Centre for Evidence-Based Medicine, Oxford, has developed several different evidence rating scales that detail evidence review standards). If you intend to compare the effectiveness of EBM and CAM to treat patients of the same illness or symptoms, in order to justify comparing two medicine systems that have different evidence systems, you need to explicitly explain the factor and variable similarities and differences, e.g. the time required to generate similar level of effectiveness, what kind of scientific evidence and measurements are used, side effects or physiological responses).