First off, anyone who tells you that they absolutely know the answer to this question is wrong.
The fact is that there are a lot of important aspects of Homeopathy that homeopaths do not understand. We accept and tolerate this, not because it is illogical or irrational -- it is not illogical -- but because the logic that underpins homeopathy is arranged differently from conventional scientific methodology. Most of what we do in homeopathy is based on what is called "inductive reasoning." Inductive reasoning is a form of logic that stays very close to observed experience. It's simply observing repeating patterns in nature, and making predictions based on those patterns. Theory or explanations are unnecessary if, based on prior results, you can predict the behavior of something from its past behavior. Homeopathy is based almost entirely on this type of inductive logic. There is a minimum of theorization, and what there is, is very closely tied to and derived from observation.
What this means is that we often don't know why something works; we just know that it does work. Homeopaths do what they do because past experimentation has demonstrated: "that if you do this thing in that specific situation, health will result."
One principle that has come out of the observation of nature is the "Law of Similars." If you present a medicine to a sick patient that is capable of creating the same symptoms in a healthy person, the sick person will get better. Based on observation of millions of cases, we believe that the medicine prods the sick person's own healing mechanisms to act appropriately in regards to the illness, and they get better.
Scientific method is a combination of inductive and deductive reasoning. In scientific method one observes nature(inductive), then tries to explain the observations with theory or thesis (deductive), then one tests the thesis through experimentation or data collection (inductive/empirical). Homeopaths do all of this, but with a different emphasis of logic.
There's really not much in the homeopath process or philosophy that involves vibration or energy as it is understood in classical physics or chemistry. But there is some of the language. When classical homeopaths talk about energy, they usually mean the energy that the body has available for healing, i.e. the Vital Force. Hahnemann, however, also speaks about homeopathic medicines having "dynamic energy," which is something very much like the Vital Force, but existing in an inanimate object. Is this a "vibration?" Is this really an "energy?" We really don't know. There's not much in classical physics or chemistry or biology that explains the results that we see.
My own practice or observations confirm Hahneman's deductiond that what is happening is that homeopathic medicines speak to the body (and mind and spirit) in what amounts to a language of existence, which includes illness. The medicines present false and transitory information about illness and environment, such that the body's healing and homeostatic mechanisms recognize and accept it as real, and then act upon it.
But as all homeopaths know, it doesn't work all the time, and sometimes that failure to work seems to be based on the potency and specific methodology of delivery of the medicine. And this is where what we do seems to look a lot more about "frequency and vibration."
When a homeopathic medicine is too strong, the client will have an "aggravation," which is a temporary worsening of existing symptoms. For the homeopath this is a good sign because aggravations can only happen if the remedy is a good match for the client's symptoms. It's just too strong. If the homeopath re-doses with a lower potency, or waits, then the aggravation will subside and the aggravated symptoms will begin to heal and improve past where they were before the medicine.
What is in the medicine that allows it to carry this information to the client's Vital Force? Personally, I think it is quantum entanglement, but there are homeopaths who believe that it has something to do with magnetic resonance. Still others believe that the transmitting medium is nanoparticles. There are decent arguments to be made for each of these three bases. I would not be surprised if the answer involves even two or all three of these notions. Or of course, it's worth mentioning that the answer could be from something that we have no grasp of whatsoever.
So where does that leave us in terms of "Vibration and Energy?" It makes sense to use these terms if they are used in a more colloquial sense, and not in the scientific senses of them. We have no direct evidence that either is in play with homeopathic medicines, just observations that might suggest that what does happen, does involve them.
But if you speak to someone who tells you that vibration and energy are the basis for how homeopathic medicines work?
Ehhh. Not so much.