In order to flask orchids, you need to provide a sterile environment, light, and nutrition. Nutrition is provided by tissue culture media - a gelatinous substance that contains water, sugar, agar, and all of the other ingredients that orchids need to germinate and grow.
If you've ever seen the ingredients list for orchid flasking medium, it quickly becomes clear that providing the right nutrition for them is a rather exacting science. Luckily, many orchid flasking media come pre-formulated and are good enough for germinating and growing many different species. But why should we ever settle for "good enough?"
To improve upon the standard orchid medium, we typically add what may be called an "undefined organic additive". That's a fancy term for common orchid media ingredients such as bananas, coconut water, pineapple juice, potatoes, etc.
That's right: baby orchids love to "eat" bananas. I remember when I heard this for the first time and I couldn't believe it. It just didn't sound very... scientific. Of course, I had to find it out for myself. I took some tiny Cattleya hybrid seedlings that I had germinated in a flask, and transferred some of them to medium with the recommended concentration of banana pulp, and some without. Sure enough, the Cattleya seedlings on the medium with banana pulp grew massive roots, and clearly outperformed their banana-lacking brethren. I then tried it with Encyclias, Dendrobiums, Vandas, Paphiopedilums, and more. The results were convincing. Of course, this leads to questions: Is it the potassium? The complex carbohydrates? Maybe someday we will know. The most important thing is that it works.
After years of flasking, reading about flasking, and talking with others in the trade, I've learned to be less skeptical when someone says, "For such and such species, you should include turnip in the medium!" Of course, I still have to find it out for myself. After all, that's the fun part!