The term 'vibrations' is often left incredibly vague. I really don't have an answer to describe what some people mean, as they'll use the term so broadly that it ends up meaning basically nothing in many cases. A vibration, in the actual sense, is an oscillation of an object and typically at a given frequency. But all too often, someone will claim some thing has "vibrations," and some even claim that a substance (take quartz as an incredibly common example) has a specific frequency of vibration. In the case of quartz, partly why this becomes so false, is that the vibration of quartz is measurable with its piezo properties and other physical properties. The actual frequency of vibration changes based on the dimensions of the quartz and the method of excitement (causing the vibration in the first place). Of course, the smaller the piece, the higher the frequency.
Now, backing away from the actual science, and meandering back to the metaphysical, the term vibration is basically synonymous with energy sympathetic to a specific purpose. Some people may claim to detect an actual buzzing from some things, while others may not.
But in a nutshell, raising vibrations is about improving the 'quality' of one's metaphysical self. And something having energy means they believe it has some corresponding energy with some aspect or other attribute.